WorldWideScience

Sample records for mikrostrukturierter magnetischer kalorimeter

  1. Development of microstructured large area magnetic calorimeters with Au:Er- and Ag:Er-sensors for the detection of x-ray quanta and high energetic particles; Entwicklung grossflaechiger mikrostrukturierter magnetischer Kalorimeter mit Au:Er- und Ag:Er-Sensoren fuer den energieaufgeloesten Nachweis von Roentgenquanten und hochenergetischen Teilchen

    Energy Technology Data Exchange (ETDEWEB)

    Burck, Andreas

    2008-11-04

    This thesis describes the development of large-area magnetic calorimeters which could for example be used for the investigation of the dissociative recombination or the measurement of the Lamb-shift for hydrogenlike heavy ions. The detectors consist of two meandershaped niobium thin film pickup coils and a paramagnetic sensor. The deposition of energy in the sensor results in a temperature change and therefore in a change of magnetisation of the sensor, which can be measured by a SQUID-magnetometer with high precision. As sensormaterials a dilute alloy of gold-erbium (Au:Er) as well as silver-erbium (Ag:Er) were used. Whereas the Ag:Er-sensor was glued on the pickup coil the Au:Er-sensor was for the first time microstructured by a novel microstructuring process established in this thesis. For the characterisation of the detectors and the sensormaterials a fluorescence source and a {sup 55}Fe source were used. The thermodynamic properties of the Au:Er-sensors thereby show promising results, as the magnetisation shows bulk properties down to 20 mK. The measurements of the signalize and the magnetisation with the detector which was equipped with a Ag:Er-sensor showed that the thermodynamic properties of the Ag:Eralloy could be fully described. Furthermore the shape of the pulses, the noise and the energy resolution of both detectors will be discussed. (orig.)

  2. Extreem-laagfrequente elektrische en magnetische velden van huishoudelijke apparatuur

    NARCIS (Netherlands)

    Kelfkens G; Pruppers MJM; LSO

    2006-01-01

    De blootstelling aan elektrische en magnetische velden ligt voor de meeste huishoudelijke apparaten onder de niveaus die de Europese Unie aanbeveelt. Voor die apparaten zijn geen gezondheidseffecten op de korte termijn te verwachten.
    Elk apparaat dat op het elektriciteitsnet is aangesloten

  3. Magnetische Anregungen und Achsenkonversion in NdCu2

    OpenAIRE

    2001-01-01

    Die Arbeit beinhaltet eine Untersuchung der magnetischen Anregungen in NdCu2 mittels inelastischer Neutronenstreuung. Die Zielsetzung besteht darin, die zur Beschreibung der magnetischen Eigenschaften notwendige Austauschwechselwirkung zu charakterisieren. Dazu wurden die Spinwellendispersionsrelationen in mehreren magnetischen Phasen gemessen (ferro-, ferri-, antiferromagnetisch; magnetische Momente parallel b). Die Lage der in der ferromagnetischen Phase F3 erwarteten zwei Dispersionszweige...

  4. Magnetic cooling. The future or utopia?; Magnetische koeling. Toekomst of utopie?

    Energy Technology Data Exchange (ETDEWEB)

    Krosse, L.; Vermeeren, R.J.F.; Verwoerd, M. [Sectie Thermische en Fysische Processen, TNO Milieu, Energie en Procesinnovatie TNO-MEP, Apeldoorn (Netherlands)

    2004-10-01

    In accordance with the Kyoto agreement the Netherlands have the ambition to reduce the greenhouse gas emissions by 50 Mton CO2-eq. during 2008-2012, compared to 1990-1995. In the field of refrigeration still a lot of greenhouse gases are being used. One option to reduce the emission of greenhouse gases is to apply an alternative refrigeration technology like magnetic cooling. Magnetic cooling is based on the reversible magneto-caloric effect (MCE). Cooling can be obtained by magnetising and demagnetising MCE-materials with permanent magnets, so very little electrical energy is needed. Furthermore, any fluid, such as water or air can be used as the heat transfer medium. Among the advantages of magnetic cooling are: silent operation, application of environmentally benign heat transfer media and energy efficiency. On the other hand it is stilt an immature technology, unknown by most manufactures, and multiple step systems are needed to bridge a sufficient temperature gradient at acceptable cooling capacities. In this study a number of system concepts were identified for magnetic cooling in conventional cooling applications such as domestic refrigerators, cabinets, mobile air-conditioners and stationary airconditioners. At this stage of the development it is essential that the feasibility of the concepts wilt be experimentally validated. Furthermore, the MCE-material research at the universities needs to be followed closely, because it will bring better systems within reach. [Dutch] In overeenstemming met de afspraken gemaakt op de klimaatconferentie in Kyoto streeft Nederland na een reductie van broeikasgas emissies met 50 Mton CO2-eq. in de periode 2008-2012 ten opzichte van 1990-1995. Binnen de koudetechniek worden nog veel broeikasgassen (HFK's) gebruikt, waarvan een deel geemitteerd wordt. Een optie om deze emissies te beperken, is het toepassen van een alternatieve koeltechnologie: magnetische koeling. Magnetische koeling is gebaseerd op het verschijnsel dat

  5. Microstructured thin film radiators as infrared sources for new gas measuring applications; Mikrostrukturierte Duennschichtstrahler als Infrarot-Strahlungsquellen fuer neue Anwendungen in der Gasmesstechnik

    Energy Technology Data Exchange (ETDEWEB)

    Vaihinger, S. [Endress und Hauser Conducta GmbH und Co., Gerlingen (Germany); Bytyn, W. [Endress und Hauser Conducta GmbH und Co., Gerlingen (Germany)

    1997-04-01

    Photometric infrared gas analysers for the low cost market are using directly modulated radiation. The mostly used glass encapsulated radiation sources are limiting the fields of application due to the absorption of the glass at wavelengths beyond 4.3 {mu}m. Microstructured thin film radiators enable new applications in the mid infrared range such as ammonia or Freon at 11 {mu}m. In addition these sources show better performance even in standard applications such as CO{sub 2} (4.24 {mu}m) at lower power consumption as compared with glass encapsulated sources. (orig.) [Deutsch] Photometrische Infrarot-Gasanalysatoren im Low-cost-Bereich arbeiten mit direkt modulierter Strahlung. Die meist verwendeten gasgekapselten Strahlungsquellen begrenzen den Anwendungsbereich durch die Transmissionseigenschaften des Glases, das fuer Infrarot nur bis 4,3 {mu}m durchlaessig ist. Mikrostrukturierte Duennschichtstrahler erschliessen nicht nur neue Anwendungen im laengerwelligen Bereich, wie z.B. Ammoniak oder Freon bei 11 {mu}m, sondern sie sind auch bei Standardanwendungen wie CO{sub 2} (4,24 {mu}m) bei deutlich geringerem Leistungsbedarf den einfachen Strahlern ueberlegen. (orig.)

  6. Melatonin - a key to the evaluation of the effects of electric; Melatonin - Schluessel fuer die Bewertung der Wirkung elektrischer und magnetischer Felder?

    Energy Technology Data Exchange (ETDEWEB)

    Wunstorf, B.; Lichtenberg, W. [Fachhochschule Hamburg (Germany). Fachbereich Oekotrophologie; Boikat, U. [BAGS, Amt fuer Gesundheit, Hamburg (Germany)

    2000-09-01

    The human pineal gland produces melatonin in a circadian rhythm. The substance has different functions - as a hormone, as an antioxidant and as a neurotransmitter. The secretion of melatonin and its tumor inhibition function can be influenced by electric and magnetic fields. Investigations have been carried out with rodents which have a melatonin rhythm similar to humans; nevertheless, they show a high variability between the species. The present state of knowledge only allows limited use of melatonin as an indicator for the impact of electric and magnetic fields. (orig.) [German] In der Epiphyse des Menschen wird in circadianem Rhythmus Melatonin produziert und ausgeschuettet. Die Substanz hat unterschiedliche Funktionen - als Hormon, Antioxidans und Neurotransmitter. Seine Ausschuettung und seine tumorhemmende Funktion koennen durch elektrische und magnetische Felder beeinflusst werden. Anhand von Nagern, die einen dem Menschen aehnlichen Melatoninrhythmus haben, allerdings eine hohe Speziesvarianz aufweisen, wurden diese Funktionen untersucht. Nach dem jetzigen Kenntnisstand eignet sich Melatonin nur bedingt als Indikator fuer die Wirkungen elektrischer und magnetischer Felder. (orig.)

  7. Extreme low-frequency electric and magnetic fields due to the use of household appliances; Extreem-laagfrequente elektrische en magnetische velden van huishoudelijke apparatuur

    Energy Technology Data Exchange (ETDEWEB)

    Kelfkens, G.; Pruppers, M.J.M.

    2005-07-01

    Exposure to electric and magnetic fields due to the use of most household appliances does not exceed the exposure levels recommended by the European Union. No short-term health effects are to be expected for these appliances. All appliances connected to the power grid are surrounded by electric and magnetic fields to which the user can be exposed. Because some people worry about possible health effects caused by this exposure, it is important to study the electromagnetic fields in the vicinity of household appliances. This report evaluates the scientific investigations of health effects that may occur in using household appliances. The legislation for the use of these appliances in both the European Union and the Netherlands is also described. Finally, an overview is given of comparative measurements with respect to the magnetic fields and exposure in the neighbourhood of household appliances. Scientific literature, which is not always up to date, suggests that for some household appliances possibly still in use, the magnetic fields will exceed the exposure levels advised by the EU. As a result of both technological improvement and the current obligation that household appliances comply with a European standard, exceeding the levels advised by the EU for appliances that come onto the market is less likely. The exposure levels recommended by the EU are based on effects that occur during or shortly afterwards exposure. It cannot be ruled out that exposure below these levels may lead to long-term health effects. However, there is no scientific evidence for a relationship between cancer and the use of household appliances. [Dutch] De blootstelling aan elektrische en magnetische velden ligt voor de meeste huishoudelijke apparaten onder de niveaus die de Europese Unie aanbeveelt. Voor die apparaten zijn geen gezondheidseffecten op de korte termijn te verwachten. Elk apparaat dat op het elektriciteitsnet is aangesloten, heeft een elektrisch en magnetisch veld om zich heen

  8. Mictrostructured sensor systems for chemical gas analysis - 'MISCHGAS'. Vol. 1: Reports 1 - 6. Final report; Mikrostrukturierte Sensorsysteme fuer die chemische Gasanalyse - 'MISCHGAS'. Bd. 1: Teilberichte 1 - 6. Abschlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1999-07-01

    The project MISCHGAS was aimed at low-power microstructured multisensor systems for analyses of complex gas mixtures. This comprised 1. the development of the sensor chip (sensor layout, sandwich sensor systems, ultrathin carrier materials, and sol-gel technologies), 2. investigation of atomistic and electrical sensor mechanism, 3. design and construction (glues, materials, noble metal free contact systems), 4. generation and reading of the sensor signal, 5. investigation of the analytical properties of the sensors, 6. user-oriented specialised gas analysis systems. [German] Ziel des Projektes MISCHGAS sind leistungsarme, mikrostrukturierte, multisensor-geeignete Systeme fuer die Analyse sowohl einzelner als auch mehrerer Kompoenten komplexer Gasgemische. Dazu wurden die notwendigen Teilbereiche: technologische Entwicklungen des Sensorchips, Klaerung atomistischer sowie elektrischer Sensormechanismen, Aufbau und Verbindungstechnik, Generierung und Auslesung des Sensorsignals, Ermittlung der analytischen Eigenschaften der Sensoren, anwenderorientierte spezialisierte Gasmesssysteme von den Verbundpartnern bearbeitet. Hauptpunkte neuer technologischer Entwicklungen waren Sensorlayout, Sensorschichtsysteme sowie ultraduenne Traegermaterialien ueber die 'porous silicon sacrificial layer'-Technik sowie Sol-Gel-Technologien. Damit konnten leistungsarme Traeger hergestellt werden. Materialien waren SnO{sub 2} und V{sub 2}O{sub 5}. Der Einfluss von Pt auf die Sensorreaktion konnte beschrieben werden. Das Verstaendnis phaenomenologischer Zusammenhaenge von Sensormechanismen und deren physikalisch-chemisch-analytischer Erfassung sowie der festkoerperphysikalischen Beschreibung wurde deutlich verbessert. Technologie und Prozesstechnik wurden auf Gesichtspunkte wie Qualitaetssicherung, und Transferierbarkeit ausgerichtet. Weitere Arbeitsbereiche sind die Gehaeuseentwicklung und Fixierung im Gehaeuse. In der AVT gab es Fortschritte bei Kleber und Aufbauhilfsstoffen

  9. Magnetisch abgeschirmte Kabine zur Aufnahme kleinster magnetischer und elektrischer Biosignale

    Science.gov (United States)

    Mager, Albrecht

    1982-08-01

    An extraordinary magnetically shielded room was designed and constructed for the Physikalisch-Technische Bundesanstalt Institut Berlin to measure extremely weak magnetic fields of the human body with SQUID-magnetometers. The inner and the outer dimensions of the cube-shaped room are 2.25 m and about 5 m. The shield has 6 magnetic shells of a high-permeability alloy and an inner shell welded of massive copper plates. The total weight of the magnetic alloy is about 10 t and about 5 t for the inner copper shell. The required shielding factor of 1000 for the very low frequencies was greatly surpassed by the real measured value of 10000 (measured without any compensating or idealizing method). With rising frequencies the shielding factor reaches higher values, at 50 Hz more than 100000 and a million for 1000 Hz. First measurements in the shielded room with high-resolution magnetocardiograms (HR MCG) and high-resolution electrocardiograms (HR ECG) showed new methods for non-invasive electrophysiological investigations in man.

  10. Self-constructed detectors for environmental radiation sources. Instruments for detecting and measuring electric and magnetic fields as well as radioactive radiation; Selbstgebaute Detektoren fuer Strahlenquellen in der Umwelt. Pruef- und Messgeraete fuer elektrische und magnetische Felder sowie radioaktive Strahlung

    Energy Technology Data Exchange (ETDEWEB)

    Lay, Peter

    2011-07-01

    The book presents experiments for detecting and measuring radiation sources. This includes detectors for electric and magnetic fields, radioactive radiation and even cosmic radiation, all of which can be detected by simple (electronic) circuits. Apart from the practical experiments, also basic physical knowledge is provided. The book comprises the following chapters: 1. Introduction; 2. Electrostatic fields in the environment; 3. Magnetostatic fields; 4. Electrodynamic fields; 5. Magnetodynamic fields; 6. Electromagnetic radiation in the environment; 7. Radioactive radiation in the environment; 8. Cosmic radiation; 9. PC interface; 10. Professional radiation measurement; 11. Risk potential. [German] In diesem Buch werden Experimente vorgestellt, mit denen man die verschiedenen Strahlenquellen nachweisen und messtechnisch erfassen kann. Darunter zaehlen Detektoren zum Nachweis elektrischer und magnetischer Felder, radioaktiver Strahlung und sogar von Strahlen aus dem Weltall. Mit einfachen (elektronischen) Schaltungen werden diese Gefahrenquellen aufgespuert. Neben vielen praxiserprobten Experimenten wird auch das physikalische Grundwissen vermittelt. Das Buch ist in folgende Kapitel aufgeteilt: 1. Einfuehrung; 2. Elektrostatische Felder in der Umwelt; 3. Magnetostatische Felder; 4. Elektrodynamische Felder; 5. Magentodynamische Felder; 6. Elektromagnetische Strahlen in der Umwelt; 7. Radioaktive Strahlen in der Umwelt; 8. Strahlen aus dem Weltall; 9. PC-Schnittstelle; 10. Professionelle Strahlenmessung; 11. Gefahrenpotenzial.

  11. Synthese und Applikation von magnetisch verformbaren Hydrogelkompositen

    OpenAIRE

    Bolle, Jens

    2011-01-01

    Als „intelligent“ bezeichnete Materialien sind in der Lage, mit steuerbaren Form- oder Eigenschaftsänderungen auf Zielreize zu reagieren, ohne dafür einen zusätzlichen Sensor zu benötigen. Man bezeichnet sie daher auch als Sensor-Aktor-Systeme. Da sie ohne äußere Sensorsysteme auskommen, können diese Werkstoffe als kleine, einfach anwendbare und preisgünstige Bauteile für eine Vielzahl von Applikationen dienen. Ihre Entwicklung gestattet sowohl die fortschreitende Miniaturisierung tech-nische...

  12. Microstructured energy harvesters for energy autonomous sensors; Mikrostrukturierte Energiewandler fuer energieautonome Sensoren

    Energy Technology Data Exchange (ETDEWEB)

    Hohlfeld, Dennis; Kamel, Talal; Altena, Geert; Su, Jiale; Elfrink, Rene; Vullers, Ruud; Schaijk, Rob van [Holst Centre/IMEC, Eindhoven (Netherlands)

    2009-07-01

    This work presents microstructured energy harvesters for powering autonomous sensors. Vibrational devices either employ the piezoelectric or electrostatic effect for energy conversion with operating frequencies from 100 to 1000 Hz. We present a wireless energy autonomous sensor system, which transmits temperature measurements every 15 seconds powered by a vibrational energy harvester. Micromachined thermocouples are considered as a cost-effective breakthrough solution for energy harvesters working at low thermal gradients and weak heat flows, typical for e.g. human body heat generation. (orig.)

  13. Herstellung und Charakterisierung mikrostrukturierter Beschichtungen mittels Ink-jet und Pad-printing

    OpenAIRE

    Danzebrink, Rolf

    2006-01-01

    Mikrooptische Systeme erhalten in unserer Zeit eine immer wichtigere Bedeutung. Es müssen dafür die bisherigen Herstellungsmethoden überdacht und nach neuen Prinzipien geforscht werden. Mikrolinsen werden in Detektoren, Glasfaserkupplungen oder auch in der Sensortechnik eingesetzt. In dieser Arbeit wird die prinzipielle Machbarkeit geprüft, Mikrolinsen mit Hilfe eines Tintenstrahl- und Tampondruck- Prozesses herzustellen, indem ein hybrid-organisch-anorganisches Sol auf einem Glassubstrat abg...

  14. Extreem-laagfrequente elektrische en magnetische velden van huishoudelijke apparatuur

    NARCIS (Netherlands)

    Kelfkens G; Pruppers MJM; LSO

    2006-01-01

    Exposure to electric and magnetic fields due to the use of most household appliances does not exceed the exposure levels recommended by the European Union. No short-term health effects are to be expected for these appliances. All appliances connected to the power grid are surrounded by electric and

  15. Magnetische Durchflusszytometrie als innovative nanomedizinische Methode zur Detektion zirkulierender Tumorzellen

    OpenAIRE

    Künzel, J; Gößwein, D; Strieth, S; Stauber, R; Matthias, C

    2015-01-01

    Einleitung: Trotz Fortschritten in der Therapie von Kopf- und Halskarzinomen stagniert die gemittelte 5-JÜR aller Tumorstadien bei etwa 50%. Zirkulierende Tumorzellen (CTC) scheinen einen unabhängigen Prognoseparameter für das frühzeitige Auftreten von Therapieresistenzen, von Metastasierung sowie das krankheitsfreie Überleben darzustellen. Technologien zur Detektion von CTCs stellen somit einen vielversprechenden Ansatz zur Optimierung des Stagings und zur Auswahl zielgerichteter Therapien ...

  16. Simulation der Energierekonstruktion der verbesserten Flüssigargon-Kalorimeter-Auslese bei ATLAS

    CERN Document Server

    AUTHOR|(SzGeCERN)758889; Zuber, Kai

    The Large Hadron Collider (LHC) at CERN is designed to accelerate particles close to the speed of light and to collide them. Several particle detectors investigate the proton-proton collisions. One of them is the ATLAS detector, which consists of different sub-detectors. The purpose of one of them, the Liquid-Argon (LAr) calorimeter, is to measure the energy of particles. The deposited energy from particles is processed, analysed and reconstructed in the end by filter algorithms in the readout electronics. Since there are many particle interactions for each bunch crossing the ATLAS detector has a trigger system to select only the interactions of physical interest. For 2018 an upgrade of the LHC and ATLAS is planned to increase the luminosity. Which is a big challenge for the trigger system. Therefore an upgrade of the readout electronics of the LAr calorimeter is planned. Simulations are used and presented to evaluate the design of the future readout electronics. In this thesis the analog pulse shapes of the ...

  17. First negative ion beam measurement by the Short-Time Retractable Instrumented Kalorimeter Experiment (STRIKE)

    Energy Technology Data Exchange (ETDEWEB)

    Serianni, G., E-mail: gianluigi.serianni@igi.cnr.it; De Muri, M.; Veltri, P.; Bonomo, F.; Chitarin, G.; Pasqualotto, R.; Pavei, M.; Rizzolo, A.; Valente, M. [Consorzio RFX, Euratom-ENEA association, Corso Stati Uniti 4, 35127 Padova (Italy); Muraro, A. [Istituto di Fisica del Plasma, Associazione EURATOM-ENEA-CNR, Milano (Italy); Franzen, P.; Ruf, B.; Schiesko, L. [Max-Planck-Institut für Plasmaphysik, D-85748 Garching bei München (Germany)

    2014-02-15

    The Source for Production of Ion of Deuterium Extracted from Rf plasma (SPIDER) test facility is under construction in Padova to optimise the operation of the beam source of ITER neutral beam injectors. The SPIDER beam will be characterised by the instrumented calorimeter STRIKE, whose main components are one-directional carbon-fibre-carbon-composite tiles. A small-scale version of the entire system has been employed in the BAvarian Test MAchine for Negative ions (BATMAN) testbed by arranging two prototype tiles in the vertical direction. The paper presents a description of the mini-STRIKE system and of the data analysis procedures, as well as some results concerning the BATMAN beam under varying operating conditions.

  18. Microstructured segmented Paul trap with tunable magnet field gradient; Mikrostrukturierte segmentierte Paul-Falle mit einstellbarem Magnetfeldgradienten

    Energy Technology Data Exchange (ETDEWEB)

    Kaufmann, Delia

    2012-02-03

    Strings of laser cooled ions stored in microstructured Paul traps (microtraps) have promising potential for quantum information science. They provide a system which can be screened from a decohering environment, accurately prepared, manipulated and state selectively detected with efficiency close to unity. Magnetic field gradients allow for addressing trapped ions in frequency space. Furthermore, coupling of the ions' motional and spin states and long range spin-spin coupling of the ions' internal states are induced by such a gradient. This method is called Magnetic Gradient Induced Coupling, MAGIC. In this thesis, the design, construction and first characterization of a novel microtrap with an integrated solenoid is reported. The solenoid is designed to create a high magnetic field gradient per dissipated heat. The microtrap consists of three layers stacked onto each other. The outer layers provide a trapping potential, while the inner layer creates the switchable magnetic field gradient. Another specialty of this trap is the 33 pairs of DC-electrodes, allowing to move the ions along the trap axis and to adjust the range and the strength of the ions' spin-spin interactions. The microtrap is fixed on top of a ceramic block that provides the necessary electrical connections via thick film printed wires, a technique adopted in the context of microtraps for the first time, and in addition acts as a vacuum interface. The volume of the vacuum chamber is quite small, allowing for pressures in the low 10{sup -11} mbar range. In this microtrap, {sup 172}Yb{sup +}-ions are trapped, cooled and shuttled over a distance of about 2 mm. Trapped ions are used as magnetic field gradient probes, with a relative magnetic field precision of {delta}B/B{sub 0}=7.10{sup -6}. The addressing of two ions with the MAGIC method in the solenoid's magnetic field gradient is demonstrated.

  19. Development of a metallic magnetic calorimeter for high resolution spectroscopy; Entwicklung eines metallischen magnetischen Kalorimeters fuer die hochaufloesende Roentgenspektroskopie

    Energy Technology Data Exchange (ETDEWEB)

    Linck, M.

    2007-05-02

    In this thesis the development of a metallic magnetic calorimeter for high resolution detection of single x-ray quanta is described. The detector consists of an X-ray absorber and a paramagnetic temperature sensor. The raise in temperature of the paramagnetic sensor due to the absorption of a single X-ray is measured by the change in magnetization of the sensor using a low-noise SQUID magnetometer. The thermodynamic properties of the detector can be described by a theoretical model based on a mean field approximation. This allows for an optimization of the detector design with respect to signal size. The maximal archivable energy resolution is limited by thermodynamic energy fluctuations between absorber, heat bath and thermometer. An interesting field of application for a metallic magnetic calorimeter is X-ray astronomy and the investigation of X-ray emitting objects. Through high-resolution X-ray spectroscopy it is possible to obtain information about physical processes of even far distant objects. The magnetic calorimeter that was developed in this thesis has a metallic absorber with a quantum efficiency of 98% at 6 keV. The energy resolution of the magnetic calorimeter is EFWHM=2.7 eV at 5.9 keV. The deviation of the detector response from a linear behavior of the detector is only 0.8% at 5.9 keV. (orig.)

  20. Magnetic semiconductors for spinelectronics. Europium sulfide and magnetically doped gallium nitride; Magnetische Halbleiter zum Einsatz in der Spinelektronik. Europiumsulfid und magnetisch dotiertes Galliumnitrid

    Energy Technology Data Exchange (ETDEWEB)

    Keller, J.

    2007-07-02

    In this work, magnetic semiconductors were investigated. As ferromagnetic compound semiconductor, EuS was investigated as thin film system. Particular attention was paid to the influence of the substrate temperature during growth on the sample properties. The samples grown and investigated here show an anomalous Hall effect. As diluted magnetic semiconductors (DMS), GaN films magnetically doped with Mn or Gd were investigated. In both material systems, ferromagnetism far above room temperature was demonstrated.While GaGdN shows a homogeneous magnetism, all ferromagnetic GaMnN samples show small clusters (phase separations). In addition, measurements of the optical absorption and the magnetic circular dichroism (MCD) were performed on the GaMnN samples. In the optical measurements, the Mn was identified as deep acceptor. At low temperatures, both the magneto-absorption and the MCD show a Zeeman-shift of an absorption band for all doping levels. The exchange energies between valence band and localized magnetic moments can be extracted from fits of the Brillouin function to the Zeeman shifts. This yields values between 1.4 eV and 1.7 eV for the lowest doping levels and between 1.7 eV and 2.1 eV for the highest doped sample. At low temperatures, no ferromagnetic behavior was found in the magneto-optical experiments. The signal is dominated by the localized Mn spin system. At room temperature, the MCD shows a ferromagnetic signature. At elevated temperatures, the signal from the Mn spin system is small enough that the influence of the clusters on the band structure of the host lattice becomes visible. Contrary to the GaMnN samples, the GaGdN films show a homogeneous magnetism. The magnetically doped GaN thin film systems investigated here exhibit different behavior. The exchange mechanism proposed for GaGdN leads to a homogeneous ferromagnetism and is similar to the magnetic exchange in the Eu chalcogenides. The interplay between this intra-atomic f-d exchange and the magnetic end electric properties was demonstrated for the EuS samples. The behavior of the GaMnN samples is contrary to the aforementioned samples. In the ferromagnetic samples, the extrinsic and intrinsic magnetic properties were separated and the magnitude of the exchange between localized magnetic states and the valence band was determined. The samples investigated here do not show the homogeneous carrier mediated ferromagnetism theoretically predicted. (orig.)

  1. Magnetic hybride layers. Magnetic properties of locally exchange-coupled NiFe/IrMn layers; Magnetische Hybridschichten. Magnetische Eigenschaften lokal austauschgekoppelter NiFe/IrMn-Schichten

    Energy Technology Data Exchange (ETDEWEB)

    Hamann, Christine

    2010-10-06

    By the lateral modification of the magnetic properties of exchange-coupled NiFe/IrMn layers soft-magnetic layers were produced, which show both new static and dynamic properties. As lateral structuration methods hereby the localoxidation as well as ion implantation were applied. By means of thes procedures it has been succeeded to mould specific magnetic domain configurations with strp structure into the layers. In dependence of the structure orientation as well as strip period the remagnetization behavior as well as the magnetic-resonance frequency and damping of the layers could directly be modified. The new dynamical properties are hereby discussed in the framework of the coupling via dynamical charges and the direct affection of the effective field of the artificially inserted domain state. The presented results prove by this the large potential of the lateral magneto-structuration for the tuning of specifical static as well as dynamic properties of magnetically thin layers.

  2. Magnetic anisotropy in GaMnAs; Magnetische Anisotropie in GaMnAs

    Energy Technology Data Exchange (ETDEWEB)

    Daeubler, Joachim

    2009-07-02

    The goal of the present work was the detailed investigation of the impact of parameters like vertical strain, hole concentration, substrate orientation and patterning on the MA in GaMnAs. At first a method is introduced enabling us to determine the MA from angle-dependent magnetotransport measurements. This method was used to analyze the impact of vertical strain {epsilon}{sub zz} on the MA in a series of GaMnAs layers with a Mn content of 5% grown on relaxed InGaAs-templates. While hole concentration and Curie temperature were found to be unaffected by vertical strain, a significant dependence of the MA on {epsilon}{sub zz} was found. The most pronounced dependence was observed for the anisotropy parameter B{sub 2} {sub perpendicular} {sub to}, representing the intrinsic contribution to the MA perpendicular to the layer plane. For this parameter a linear dependence on {epsilon}{sub zz} was found, resulting in a strain-induced transition of the magnetic easy axis with increasing strain from in-plane to out-of-plane at {epsilon}{sub zz} {approx} -0.13%. Post-growth annealing of the samples leads to an outdiffusion and/or regrouping of the highly mobile Mn interstitial donor defects, resulting in an increase in both p and T{sub C}. For the annealed samples, the transition from in-plane to out-of-plane easy axis takes place at {epsilon}{sub zz} {approx} -0.07%. From a comparison of as-grown and annealed samples, B{sub 2} {sub perpendicular} {sub to} was found to be proportional to both p and {epsilon}{sub zz}, B{sub 2} {sub perpendicular} {sub to} {proportional_to} p .{epsilon}{sub zz}. To study the influence of substrate orientation on the magnetic properties of GaMnAs, a series of GaMnAs layers with Mn contents up to 5% was grown on (001)- and (113)A-oriented GaAs substrates. The hole densities and Curie temperatures, determined from magnetotransport measurements, are drastically reduced in the (113)A layers. The differences in the magnetic properties of (113)A- and (001)-GaMnAs resulting from this have been used to realize quasi-planar GaMnAs structures consisting laterally confined regions with different magnetic materials. For this purpose, mesa stripes along the [1 anti 10] direction with (113)A sidewalls were prepared on GaAs-(001) substrates. Magnetoresistance measurements clearly revealed the lateral coexistence of areas with (001)- and (113)A-specific properties. In general, patterning of GaMnAs layers results in a change of shape anisotropy and in (partial) relaxation processes in the GaMnAs structures. We found the anisotropy contribution resulting from anisotropic relaxation to be dominant. As a consequence, the magnetic easy axis for the tensile strained samples is oriented perpendicular to the wire direction within the sample plane for wire widths {<=} 3 {mu}m. (orig.)

  3. Origin of ferromagnetism in diluted magnetic semiconductors; Moegliche Ursachen des Ferromagnetismus verduennter magnetischer Halbleiter

    Energy Technology Data Exchange (ETDEWEB)

    Biegger, E.

    2007-02-14

    In this work Mn-doped Ge single crystals and thin films of the metal doped oxidic semiconductors ZnO and SnO{sub 2} were prepared and investigated in detail. Structural, magnetic, and electronic properties of Mn-doped Ge single crystals (0

  4. Magnetisches Tracking für die Navigation mit dem da Vinci® Surgical System

    Science.gov (United States)

    Nickel, Felix; Wegner, Ingmar; Kenngott, Hannes; Neuhaus, Jochen; Müller-Stich, Beat P.; Meinzer, Hans-Peter; Gutt, Carsten N.

    In dieser Studie wurde untersucht ob in einem typischen OP-Aufbau mit dem da Vinci® Telemanipulator elektromagnetisches Tracking für die Realisation eines Navigationssystems eingesetzt werden kann. Hierfür wurde in einem realen OP-Aufbau untersucht, wie stark metallische und ferromagnetisch wirksame Objekte wie Operationstisch und Telemanipulator das elektromagnetische Feld des Trackingsystems beeinflussen. Die Ergebnisse zeigen, dass der Telemanipulator nur unwesentlich die Störung des Magnetfeldes durch den OP-Tisch verstärkt. Insbesondere die Bewegung der Instrumente im Trackingvolumen verursachte keine zusätzliche relevante Störung des Magnetfeldes. Bei Begrenzung des Trackingvolumens auf eine Länge von 190 mm, Höhe von 200mm und Breite von 400 mm war der maximale Fehler in diesem Bereich an allen Messpunkten kleiner 10 mm. Der Einsatz von elektromagnetischem Tracking für die Navigation mit dem da Vinci® Surgical System ist somit in einem begrenzten Arbeitsvolumen mit hinreichender Genauigkeit möglich.

  5. SQUIDs for the characterization of magnetic nanoparticles; SQUIDs fuer die Charakterisierung magnetischer Nanoteilchen

    Energy Technology Data Exchange (ETDEWEB)

    Guillaume, Alexander

    2015-07-01

    Magnetic nanoparticles (MNP) are superparamagnetic particles with a core diameter in the nm-range. The MNPs have manifold properties which make them an interesting tool for various applications. Certain parameters, such as size or size distribution and structural properties, must be well known for these applications. In this work, the dynamic behavior of MNPs was investigated by magnetorelaxometry (MRX) at a temperature of 77 K. MRX is based on the alignment of the moment of individual MNPs in parallel to a large enough magnetization field. After switching of the field, the magnetization decays with a characteristic time constant. The measurement of the relaxation can e.g. be used to calculate the size distribution of a given MNP sample. Superconducting quantum interference devices (SQUID) based on the high-T{sub c} superconductor yttrium barium copper oxide (YBCO) were employed in this work as sensors for the magnetic field. The fabrication of the superconducting and isolating thin films was carried out by pulsed laser deposition (PLD) and optimized by methods of experimental design. Several types of directly coupled SQUIDs were fabricated from the thin films by optical lithography and argon ion etching. An existing MRX setup with fluxgates was modified to allow measurements with the directly coupled SQUIDs at 77 K. After the characterization of the system, MRX measurements were performed. The relaxation of an amount of approximately 100 billion MNPs was detected at a distance of 5 mm to the SQUID. In order to reduce the minimum detectable amount of MNPs and to minimize disturbances, a novel type of SQUID was developed, fabricated and characterized. A compensation factor of up to 195 was experimentally demonstrated with this self-compensating SQUID. MNP samples were prepared directly on the SQUID by electron beam lithography. Thereby, an amount of 167 MNPs could be detected. The limit for the measurement setup was evaluated as 58 MNPs. Finite element method (FEM) simulations were used to verify the MNP amount for the MRX measurements.

  6. Fabrication and analysis of ordered magnetic cobalt nanoparticles; Herstellung und Untersuchung geordneter magnetischer Kobaltnanoteilchen

    Energy Technology Data Exchange (ETDEWEB)

    Zuern, Klaus P.

    2009-12-17

    In the dissertation on hand monodisperse, wellordered magnetic cobalt and cobalt hydride nanoparticles have been produced and investigated magnetically. The preparation was achieved by diblock-copolymer-micelles filled with cobalt salt, from which nanoparticles of elementary cobalt respectively cobalt hydride were generated in different steps of the procedure. It was evident that the cobalthydride generated by the hydrogen plasma was surprisingly stable. It could even be taken into consideration as a hydrogen storage device for fuel cell. The magnetic properties of the particles has been investigated by x-ray magnetic circular dichroism (XMCD). In addition it was evident, that it was principally impossible to investigate a film layered on a substrate with a SQUID-magnetometer, if this film produces only a small signal as well absolutely as relatively to the magnetically measured total moment of the sample. (orig.)

  7. Nichtinvasive Magnetresonanz- Perfusionsmessung des Gehirns mittels Magnetischer Blutbolusmarkierung (Spin-Labeling)

    OpenAIRE

    Warmuth, Carsten

    2003-01-01

    Arterial spin labeling methods allow to determine quantitative tissue blood flow values noninvasively. Arterial blood is labelled by an inversion pulse and the distribution of this intrinsic tracer is measured using magnetic resonance imaging. Experiments using an extra corporal in-vitro porcine kidney in a MR compatible set-up were carried out to determine the accuracy of blood flow values calculated from arterial spin labeling measurements. In a study of 36 brain tumor patients, spin labeli...

  8. Cobalt-doped ZnO as dilute magnetic semiconductor; Cobalt dotiertes ZnO als verduennter magnetischer Halbleiter

    Energy Technology Data Exchange (ETDEWEB)

    Gacic, Milan

    2009-04-24

    Dilute magnetic semiconductors (DMS) are technologically promising materials that show ferromagnetic as well as semiconducting properties. These are one of the crucial compounds concerning the development of spintronic devices. The main problem so far ist that for applications the Curie temperature of most of the DMS compounds is much too low. However, DMS compounds based on ZnO as Zn{sub 1-x}Co{sub x}O seem to show ferromagnetism above room temperature, but the ferromagnetic exchange is not fully understood. Intensive experimental investigations need to be done. In the course of this theses Zn{sub 0.95}Co{sub 0.05}O thin films were fabricated by pulsed laser deposition and investigated concerning their magnetic, magnetoelectric and structural properties in order to understand the ferromagnetism in this material. Different experimental methods have been used, as magnetometry, X-ray diffraction (XRD), X-ray magnetic circular dichroism (XMCD), electron spin resonance (ESR) and magnetoelectric transport measurements. At special preparation conditions, where a high defect density is induced, the samples are clearly ferromagnetic above room temperature with a saturation magnetization of 2 {mu}{sub b}/Co and a remanence of 90%. Electrical transport measurements show a clear magnetoresistance as well as a anomalous Hall effect. The anomalous Hall effect rises with the magnetization indicating intrinsic ferromagnetism and a certain degree of spin polarization. As the ferromagnetism disappears with rising charge carrier density the ferromagnetic interaction cannot be mediated by the conduction electrons. A more precise evaluation of the magnetoelectric results shows that there is an additional conducting impurity band which could even be spinpolarized. So there are indications that the ferromagnetism is due to magnetic polarons. Some of the structural and magnetometric results as well as the electron spin resonance measurements suggest an additional extrinsic contribution to the ferromagnetic moment which is due to metallic Cobalt segregations. This contribution could be much higher than the intrinsic one. However, XMCD measurements show that Cobalt is not contributing to the ferromagnetism at all. All things considered, there are indications that magnetic defects play a crucial role in the magnetism of Zn{sub 0.95}Co{sub 0.05}O. (orig.)

  9. Magnetic thermotherapy of breast tumors: an experimental therapeutic approach; Magnetische Thermotherapie von Tumoren der Brust: ein experimenteller Therapieansatz

    Energy Technology Data Exchange (ETDEWEB)

    Hilger, I.; Kaiser, W.A. [Inst. fuer Diagnostische und Interventionelle Radiologie des Klinikums der Friedrich-Schiller-Univ. Jena (Germany); Andrae, W.; Hergt, R.; Hiergeist, R. [Inst. fuer Physikalische Hochtechnologie e.V., Jena (Germany)

    2005-04-01

    The therapeutic strategy for breast cancer is changing, especially for early tumor stages with good prognosis. One potential minimally invasive therapy modality consists in the accumulation of a well-tolerated magnetic material (iron oxides, particularly magnetite) in the target tissue. By applying an alternating magnetic field, energy is selectively absorbed and induces harmful heating of the tumor. The present review deals with the essential conditions and parameters as studied in vitro and in vivo in animal experiments. Extrapolations to the clinical situation are discussed, in particular, the heating potential of the magnetic material, the selection of the magnetic field parameters, the occurrence of eddy currents, the generation of localized heating spots and the expected temperature rises and their effects on the tumor area. (orig.)

  10. Mass-selected iron-cobalt alloy clusters. Correlation of magnetic and structural properties; Massenselektierte Eisen-Kobalt-Legierungscluster. Korrelation magnetischer und struktureller Eigenschaften

    Energy Technology Data Exchange (ETDEWEB)

    Bulut, Furkan

    2008-10-13

    In this work, I present results concerning structural and magnetic properties of massselected iron-cobalt alloy clusters with diameters between 5 and 15 nm. I have studied the structure of FeCo alloy clusters with high resolution transmission electron microscopy (HRTEM) and scanning tunneling microscopy (STM). I have also investigated the crystalline structure of pure iron and pure cobalt clusters with HRTEM to ensure a reliable determination of the lattice parameter for the alloy clusters. The FeCo nanoparticles have a truncated dodecahedral shape with a CsCl-structure. The clusters were produced with a continuously working arc cluster ion source and subsequently mass-selected with an electrostatic quadrupole deflector. The composition of the alloy clusters was checked with energy dispersive x-ray spectroscopy (EDX). The lateral size distribution was investigated by TEM and the height of the deposited FeCo clusters on the (110) surface of tungsten was determined by STM. Comparing the results I have observed that the supported clusters were flattened due to the high surface energy of W(110). The decrease in height of the mass-selected supported clusters amounts to about 1 nm. Furthermore, element specific magnetic studies performed by means of X-ray magnetic circular dichroism (XMCD) have shown that magnetic moments of Fe{sub 50}Co{sub 50} alloy clusters are in good agreement with the theoretically expected values in the bulk. I have also examined the behavior of the alloy clusters at elevated temperatures. The clusters exhibit an anisotropic melting on the W(110) surface. (orig.)

  11. Structural and magnetic properties of FePt nanoparticles from the gas phase; Strukturelle und magnetische Eigenschaften von FePt-Nanopartikeln aus der Gasphase

    Energy Technology Data Exchange (ETDEWEB)

    Dmitrieva, O.

    2007-09-21

    In this work, we present the structural and magnetic characterization of FePt nanoparticles. The nanoparticles with mean size of about 6 nm were prepared by sputtering in the gas and subsequent inert gas condensation. The particles are annealed in the furnace during their flight prior to deposition on a substrate. The aim of this work is to prepare magnetically hard FePt nanoparticles in the L1{sub 0}-ordered phase. The structure of the particles was investigated by high-resolution transmission electron microscopy, and the investigations were supported by contrast simulations. The morphology of the particles varies with the sputter-gas pressure and with the annealing temperature. At a pressure of 0.5 mbar, the FePt-nanoparticles are multiply-twinned with an icosahedral structure and exhibit no formation of the L1{sub 0}-ordered phase. At a higher pressure of 1 mbar and an annealing temperature of 1000 C, the particles are partially single-crystalline. About 36 % of the particles are found to be in the L1{sub 0}-ordered state as was estimated by statistical counting supported by simulations. In order to activate the volume diffusion in the particles and to stabilize the formation of the L1{sub 0}-ordered state, the addition of nitrogen was used during the sputtering phase. In this phase, atomic nitrogen is incorporated interstitially into the structure of the primary particles. After annealing nitrogen effuses out of the particles and, thereby, increases the volume diffusion of the Fe and Pt atoms. The incorporation of nitrogen atoms during nucleation and their effusion at an annealing temperature of 1000 C was verified by electron energy loss spectroscopy (EELS) and X-ray absorption spectroscopy (XAS). Structural investigations on particles prepared in the presence of nitrogen shows that most of the particles are single-crystalline and about 70 % of them are L1{sub 0}-ordered. Detailed structural analysis of the nanoparticles was done by the exit wave reconstruction method. An expansion of about 10% of the outer shells of the particles was observed. This expansion can be attributed to the oxidation of the surface of the particles. The thickness of the oxide shell was estimated by EELS and XAS to be about 1-2 atomic layers. Using X-ray magnetic circular dichroism the spin and orbital magnetic moments and the magnetization loop corresponding to Fe atoms were obtained. The enhanced value of the orbital magnetic moment of 0.2 {mu}{sub B} observed in the particles can be attributed to the tetragonal distortion of the L1{sub 0}-ordered lattice. (orig.)

  12. Quantitative imaging of magnetic nanoparticles by magneto-relaxometric tomography for biomedical applications; Quantitative Bildgebung magnetischer Nanopartikel mittels magnetrelaxometrischer Tomographie fuer biomedizinische Anwendungen

    Energy Technology Data Exchange (ETDEWEB)

    Liebl, Maik

    2016-11-18

    Current biomedical research focuses on the development of novel biomedical applications based on magnetic nanoparticles (MNPs), e.g. for local cancer treatment. These therapy approaches employ MNPs as remotely controlled drug carriers or local heat generators. Since location and quantity of MNPs determine drug enrichment and heat production, quantitative knowledge of the MNP distribution inside a body is essential for the development and success of these therapies. Magnetorelaxometry (MRX) is capable to provide such quantitative information based on the specific response of the MNPs after switching-off an applied magnetic field. Applying a uniform (homogeneous) magnetic field to a MNP distribution and measuring the MNP response by multiple sensors at different locations allows for spatially resolved MNP quantification. However, to reconstruct the MNP distribution from this spatially resolved MRX data, an ill posed inverse problem has to be solved. So far, the solution of this problem was stabilized incorporating a-priori knowledge in the forward model, e.g. by setting priors on the vertical position of the distribution using a 2D reconstruction grid or setting priors on the number and geometry of the MNP sources inside the body. MRX tomography represents a novel approach for quantitative 3D imaging of MNPs, where the inverse solution is stabilized by a series of MRX measurements. In MRX tomography, only parts of the MNP distribution are sequentially magnetized by the use of inhomogeneous magnetic fields. Each magnetizing is followed by detection of the response of the corresponding part of the distribution by multiple sensors. The 3D reconstruction of the MNP distribution is then accomplished by a common evaluation of the distinct MRX measurement series. In this thesis the first experimental setup for MRX tomography was developed for quantitative 3D imaging of biomedical MNP distributions. It is based on a multi-channel magnetizing unit which has been engineered to generate a time-multiplexed sequence of precise magnetic fields for spatially constrained magnetizing of the MNP distribution. The unit has been integrated into a sensor system containing 304 superconducting quantum interference devices (SQUIDs) used for the spatially resolved detection of the MNP responses after each magnetizing. Furthermore, for evaluation of MRX tomography MNP phantoms reflecting the MNP distribution after magnetic drug targeting therapy in animals were designed and implemented. Using these phantoms, MNP distributions with clinical MNP doses in the milligram range could be quantitatively reconstructed by MRX tomography within a field of view up to 600 cm³ and a spatial resolution of a few cubic centimeters. The deviation between the quantified and nominal MNP amount was found to be below 10%. With the present experimental setup MRX tomography measurements of a complete MNP distribution were performed within the typical anesthesia time interval of a few minutes prevailing in preclinical animal studies. By implementing advanced magnetizing sequences this measurement time of the MRX tomography setup could be reduced to below 30 s. Finally, using the same MRX tomography setup a binding state specific quantitative imaging of MNP distributions was achieved by incorporating the temporal MNP relaxation behavior into the reconstruction. Hence, MRX tomography has the potential to image the influence of the local biological environment on the physical properties of the MNPs. The presented MRX tomography setup allows for sensitive and specific spatially resolved 3D quantification of MNPs in small animals. This represents an important step towards the development of a clinical imaging tool for the control and assessment of MNP based cancer treatments. Moreover, by adjusting the excitation coils the field of view could be easily enlarged making MRX tomography quite conceivable for human application.

  13. Low frequency electric and magnetic fields; 'Electrosmog' - imagination or reality. Niederfrequente elektrische und magnetische Felder; ''Elektrosmog'' - Dichtung oder Wahrheit

    Energy Technology Data Exchange (ETDEWEB)

    Haubrich, H.J. (Technische Hochschule Aachen (Germany). Inst. fuer Elektrische Anlagen und Energiewirtschaft)

    1993-11-01

    The author tries to give an objective survey and evaluation of the present state of knowledge. His explanations are restricted to the field of low frequency, where the electrical fields depend exclusively on the voltage and the magnetic fields depend exclusively on the current. Their coupling properties are completely negligible in the dimensions to be considered here - where they differ appreciably from electromagnetic fields. One should pay attention to this in all discussions, because this is a pre-condition for low frequency fields of electrical energy supply plants and equipment being always bound to objects and carried in cables, and that they cannot be radiated to the environment, as in the high frequency range. (orig./MG)

  14. Influence of disorder and interfaces on electronic and magnetic properties of Heusler systems; Einfluss von Unordnung und Grenzflaechen auf elektronische und magnetische Eigenschaften von Heusler-Systemen

    Energy Technology Data Exchange (ETDEWEB)

    Krumme, Bernhard

    2012-07-17

    A Moessbauer-spectroscopic investigation of Fe{sub 3} films on GaAs(100) and MgO(100) revealed a disordered growth mode of Fe{sub 3}Si on GaAs(100), which is caused by an interdiffusion of Ga/As atoms. Implementing a 3 nm thick MgO tunnelbarrier on the GaAs suface inhibits the interdiffusion and enables an epitaxial film growth of Fe{sub 3}Si. By comparing experimental X-ray absorption measurements with DFT calculations we are able to resolve the contribution of the different Fe sublattices to the XAS and XMCD signal. Taking into account atomic disorder arising from Ga/As atoms within DFT calculation yields a small reduction of the spin polarization of Fe{sub 3}Si, indicating that the system Fe{sub 3}Si/GaAs(100) still is an interesting candidate for spintronic applications. For the Heusler compounds Co{sub 2}MnSi and Co{sub 2}FeSi the influence of the 3d transition metals Mn/Fe on the hybridization was determined by X-ray absorption and DFT calculations. A depth-selective study of the electronic structure of Mn in Co{sub 2}MnSi at the vicinity to a MgO tunnelbarrier indicates an increased number of unoccupied d states referring a MnSi terminated interface. The electronic structure of Si-rich Co{sub 2}FeSi depends on the external magnetic field. This points to magnetostrictive effects in this compound. Furthermore, the Heusler compound Ni{sub 51.6}Mn{sub 32.9}Sn{sub 15.5} was studied in this work. The compound is a shape memory alloy exhibiting a large inverse magnetocaloric effect. In this work the focus was put on the element-specific magnetic properties of Ni and Mn. For Mn a strong increase of the ratio of orbital to spin magnetic moment m{sub l}/m{sub S} was observed. In the austenite phase this ratio accounts for 5 %, whereas in the martensite this value becomes 13.5 %. For Ni m{sub l}/m{sub S} is almost constant at 28 %. applying a magnetic field of 3 T in the martensite phase leads to a reduction of m{sub l}/m{sub S} for both elements, indicating a field-induced reverse martensitic transition (FIRMT).

  15. Magnetic properties of the alloy system Fe-Pt. Bulk materials and nanoparticles; Magnetische Eigenschaften des Legierungssystems Fe-Pt. Volumenmaterialien und Nanopartikel

    Energy Technology Data Exchange (ETDEWEB)

    Antoniak, C.

    2007-12-14

    Besides the determination of magnetic properties of epitaxial grown Fe{sub x}Pt{sub 1-x} films like e.g. the magnetic anisotropy, effective magnetisation, exchange length and damping as reference data, wet-chemically synthesised spherical Fe{sub x}Pt{sub 1-x} nanoparticles with different sizes, compositions and crystal structures were examined systematically after the reduction of Fe oxides by a hydrogen plasma treatment. Organic ligands surrounding the particles after the synthesis, were removed as well during this procedure. These ligands prevent the agglomeration of the nanoparticles when deposited onto a substrate, but do not have any measurable effect on the oxide formation under air exposure and do not change the magnetic properties of oxidised nanoparticles within experimental error bars. Static and dynamic magnetic properties were determined using the ferromagnetic resonance technique and themeasurement of the x-ray absorption, especially the analysis of the X-ray circular dichroism. The analysis of the element-specific magnetic moments shows that the effective magnetic spin moment ({mu}{sup eff}{sub s}) of the Fe{sub x}Pt{sub 1-x} nanoparticles is reduced by 20.30% with respect to the one of the corresponding Fe{sub x}Pt{sub 1-x} film due to the inhomogeneous composition within the nanoparticles which was found by the analysis of the extended X-ray absorption fine structure. With decreasing particle size, {mu}{sup eff}{sub s} is further decreasing while the ratio of orbital-to-effective-spin magnetic moment ({mu}{sub l}/{mu}{sup eff}{sub s}) increases. Annealing at 600 C of a sample consisting of Fe{sub 0.50}Pt{sub 0.50} nanoparticles with a mean diameter around 6 nm yields a strong increase of the {mu}{sub l}/{mu}{sup eff}{sub s} ratio at the Fe sites: it reaches a value of about 9% and is as large as the value at the Pt sites. This is accompanied by an enhancement of the coercive field from (36{+-}5) mT to (292{+-}8) mT after annealing that can be explained by an increase of the effective anisotropy from 5.5 x 10{sup 4}J/m{sup 3} to 3.85 x 10{sup 5}J/{sup 3} due to the (partial) transformation to the chemically ordered phase. The effective anisotropy of very small Fe{sub 0.70}Pt{sub 0.30} nanoparticles with a mean diameter of 2.5 nm show a strong temperature dependence due to thermal fluctuations which was measured using the ferromagnetic resonance technique. The damping of the magnetisation precession in such measurements is increasing with increasing Pt content in agreement to the composition dependence of the damping in Fe{sub x}Pt{sub 1-x} films. (orig.)

  16. Magnetic excitations and axis conversion in NdCu{sub 2}; Magnetische Anregungen und Achsenkonversion in NdCu{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Kramp, S.

    2000-07-01

    The spin wave dispersion relations have been measured in several magnetic phases of NdCu{sub 2}. The results form a data base that allows to test current and future models of the anisotropic magnetic exchange interaction in RCu{sub 2} compounds by means of experimental results.

  17. Hith resolution {beta}-spectroscopy of the isotope {sup 36}Cl using magnetic calorimeters; Entwicklung magnetischer Mikrokalorimeter fuer die hochaufloesende Spektroskopie des {beta}-Emitters {sup 36}Cl

    Energy Technology Data Exchange (ETDEWEB)

    Rotzinger, H.

    2006-12-13

    This thesis describes the development of a high resolution magnetic calorimeter for the detection of the {beta}-spectrum of the isotope {sup 36}Cl with endpoint energy of 709.6 keV. The temperature rise of a metallic paramagnetic sensor due to an energy deposition is sensed by measuring its magnetization using a sensitive DC-SQUID magnetometer. For a high detection efficiency an 4{pi} gold absorber was used. The heat capacity and the geometry of the absorber is optimally matched by a flat sensor and an optimized meander shaped readout coil. The fabrication of the superconducting structures and the detector setup are described. In addition, the relevant noise sources, the energy resolution and the quantum efficiency are discussed. A measured {sup 36}Cl-spectrum with an energy resolution of {delta}E{sub FWHM}=750 eV is presented and compared with existing experimental and theoretical data. (orig.)

  18. Untersuchungen an Eisen- und Lanthanoidhaltigen Koordinationsclustern mit Triazolat- sowie Semiquinonato-Liganden

    OpenAIRE

    Kriese, Thomas

    2016-01-01

    Magnetische Untersuchungen an Lanthanoiddimeren mit Semiquinonato-Liganden. Gemischtvalente Eisen-Koordinationsclustern. Lanthanoid-Koordinationscluster mit zwölf Lanthanoiden aber mit verschiedenen Clusterladungen.

  19. Nanopatterning of Co/Pt-multilayers via self-assembled block-copolymer micelles; Magnetische Nanostrukturen basierend auf Co/Pt-Multilagen, hergestellt mittels selbstorganisierter Masken aus Blockcopolymer-Micellen

    Energy Technology Data Exchange (ETDEWEB)

    Stillrich, H.

    2007-07-01

    The production and characterization of magnetic nanostructures based on Co/Ptmultilayers are described in this thesis. Nanostructure arrays of Co/Pt multilayer films are generated utilizing the self-assembly of block copolymer micelles with a few 10nm diameter. For an understanding of the magnetic properties of nanostructures the properties of Co/Pt-multilayer films are examined first. The films are grown via different sputter techniques. The structural and magnetic properties are investigated depending on the deposition technique. The sources of magnetic anisotropy are discussed based on these investigations. One major topic concerning Co/Pt-multilayers is the reorientation of the easy axis of magnetization from perpendicular to in-plane as a function of the cobalt and platinum layer thicknesses. Combining averaging magnetization measurements and high resolution magnetic imaging, the canting of magnetization within the reorientation transition and a canted domain structure were found. The basis for magnetic nanostructures are Co/Pt-multilayers that were optimized for strong magnetic anisotropy. Magnetic antidot and dot arrays are generated from Co/Pt-multilayers via novel methods utilizing block copolymer micelle masks and ion milling. The generation of nanostructure arrays is proven by the morphologic and topographic properties, combined with the evolution of magneto-optic signals. Two different approaches for the generation of antidot arrays are shown. The magnetic properties of antidot arrays with perpendicular and in-plane easy magnetization are investigated. Magnetic dot arrays are produced utilizing the cores of SiO{sub 2} filled block copolymer micelles. The dot arrays consist of single domain particles. The switching field distribution of the dot arrays is analysed and described using the size distribution of the magnetic particles. Magnetic nanostructures in the region of the superparamagnetic limit are investigated. (orig.)

  20. High field MR imaging: magnetic field interactions of aneurysm clips, coronary artery stents and iliac artery stents with a 3.0 Tesla MR system; Hochfeld-Magnetresonanztomographie: Magnetische Anziehungs- und Rotationskraefte auf metallische Implantate bei 3,0 T

    Energy Technology Data Exchange (ETDEWEB)

    Sommer, T.; Schmiedel, A.; Hackenbroch, M.; Hofer, U.; Urbach, H.; Traeber, F.; Schild, H. [Radiologische Univ. Bonn (Germany); Maintz, D. [Radiologische Univ. Muenster (Germany); Pavlidis, C. [Klinik fuer Neurochirurgie, Univ. Bonn (Germany); Hoeher, M. [Medizinische Univ. II Ulm (Germany)

    2004-05-01

    Purpose: to evaluate magnetic field interactions of commonly used biomedical implants at 3.0 tesla. Materials and methods: fourteen aneurysm clips designed for permanent placement in intracranial aneurysms, 19 coronary artery stents and 20 iliac artery stents were evaluated in an actively shielded compact 3.0 T MR system (Intera, Philips Medical Systems, Best, the Netherlands, length of magnet 1.57 m). The magnetic deflection forces (translational movement) were evaluated as follows: the implants were suspended by a fine string and placed in the magnet bore at the location of the maximum magnetic field gradient. The translational forces F{sub z} were calculated from the measured angle of deflection from the vertical axis. The magnetic field-induced torque (rotational forces) was evaluated as follows: each implant was placed in the center of the magnetic bore parallel to the static magnetic field B0 (position 0 ). Any possible displacement of the implant was noted on a millimeter scale and any torque qualitatively evaluated using a 5 point grading scale (0: no torque; + 4: very strong torque). The implant was turned in steps of 45 , and the procedure was repeated to encompass a full 360 rotation. Results: in 52 of the 53 devices tested, the deflection force (deflection angle: range 0-21 , translational force: range 0-3.8 mN) was less than the gravitational force (i.e., the implant's weight). These devices (n = 52/53) did not show any alignment to or rotation in the magnetic field at any of the various 45 -increment positions corresponding to a qualitative torque evaluation of grade 0/4. One device (n = 1/53), an iliac artery stent made of stainless steel (Zenith, Cook, Moenchengladbach, BRD), was found to have deflection forces (deflection angle 88 translational force 299 mN) greatly exceeding the gravitational force as well as a pronounced torque (grade 4/4). (orig.) [German] Ziel: Die In-vitro-Evaluierung verschiedener biomedizinischer Implantate hinsichtlich der auf sie wirkenden magnetischen Anziehungs- und Rotationskraefte an einem 3,0-Tesla-MRT-System. Methode: Es wurden 53 metallische Implantate (14 intrakranielle Aneurysmaclips, 19 Koronararterien- sowie 20 Iliakalarterienstents) an einem 3,0-Tesla-MRT-System (Gyroscan Intera 3.0 T, Philips) untersucht. Die Bestimmung der auf die Implantate im statischen Magnetfeld wirkenden Translationskraefte F{sub z} erfolgte mithilfe des Fadentests ueber die Messung der Deflektionswinkels {beta}. Die Evaluierung der Rotationskraft F{sub rot} erfolgte qualitativ mit einer 5-Punkte-Graduierung (Grad 0: keine Rotationskraft, Grad 4: starke Rotationskraft). Ergebnisse: Bei 52 von 53 getesteten Implantaten blieb die Translationskraft F{sub z} unterhalb der auf das jeweilige Implantat wirkenden Gravitationskraft ({beta}: 0-21 , F{sub z}: 0-3,8 mN). Bei keinem dieser 52 Implantate wurde eine Rotation relativ zum Magnetfeld B{sub 0} (Rotationskraft Grad 0/4) beobachtet. Bei einem Implantat, einem Iliakalarterienstent aus Edelstahl (Zenith, Fa. Cook), wurde ein Deflektionswinkel {beta} von 88 gemessen, entsprechend einer Translationskraft F{sub z} von 299 mN, die dem 29fachen der auf das Implantat wirkenden Gravitationskraft entspricht. Hierzu konkordant zeigten sich in der qualitativen Evaluierung deutliche auf diesen Stent wirkende Rotationskraefte Grad 4/4. (orig.)

  1. Electronic and magnetic phase separation in EuB{sub 6}. Fluctuation spectroscopy and nonlinear transport; Elektronische und magnetische Phasenseparation in EuB{sub 6}. Fluktuationsspektroskopie und nichtlinearer Transport

    Energy Technology Data Exchange (ETDEWEB)

    Amyan, Adham

    2013-07-09

    The main topics of this thesis are electrical, stationary, and time-resolved transport measurements on EuB{sub 6} as well as the further development of measuring methods and analysis procedures of the fluctuation spectroscopy. The first part of this thesis was dedicated to the further development of the already known measuring methods under application of a fast data-acquisition card. The second part deals with the electrical transport properties of EuB{sub 6} and the understanding of the coupling between charge and magnetic degrees of freedom. By means of resistance and nonlinear-transport measurements as well as fluctuation spectroscopy hypotheses of other scientists were systematically verified as well as new knowledge obtained. The magnetoresistance was studied as function of the temperature in small external magnetic fields between 1 mT and 700 mT. Measurements of the third harmonic resistance as function of the temperature show maxima at T{sub MI} and T{sub C}. Electrical-resistance fluctuations were measured without external magnetic field between 5 and 100 K as well in presence of a magnetic field between 18 K and 32 K. At constant temperature measurements of the spectral power density in external magnetic fields were performed in the temperature range from 18 K to 32 K. Highly resolving measurements of the thermal expansion coefficient showed a very strong coupling of the magnetic (polaronic) degrees of freedom to the crystal lattice.

  2. Electromagnetic fields from the environment, or EMC for man. On the effect of electric, magnetic, and electromagnetic fields on man; EMVU, die EMV fuer den Menschen, ueber die Wirkungen elektrischer, magnetischer und elektromagnetischer Felder auf den Menschen

    Energy Technology Data Exchange (ETDEWEB)

    David, E. [Univ. Witten/Herdecke, Inst. fuer Normale und Pathologische Physiologie, Witten (Germany); Reissenweber, J. [Univ. Witten/Herdecke, Inst. fuer Normale und Pathologische Physiologie, Witten (Germany); Peier, D. [Univ. Dortmund, Inst. fuer Hochspannungstechnik (Germany)

    1994-12-31

    The increasing use of electrotechnical equipment causes enhanced exposure of the environment to electromagnetic fields. The impact of such fields on biological systems and on man is difficult to assess because of its complexity. In the first part the article gives an overview of the effect of electromagnetic fields on melatonin production in man, dealing specifically with the importance of melatonin for the night-and-day rhythm, sleep, the immune system, as a hormone antagonist, and for the development and growth of tumors. In a second part the authors discuss possible effects on electronic implants, especially cardiac pacemakers. (MG) [Deutsch] Die zunehmende Nutzung elektrotechnischer Einrichtungen fuehrt dazu, dass die Umwelt in steigendem Mass elektromagnetischen Feldern ausgesetzt ist. Die Ermittlung der Auswirkungen dieser Felder auf biologische System und auf den Menschen erweist sich aufgrund ihrer Komplexitaet als schwierig. In einem ersten Teil gibt der Artikel einen Ueberblick ueber die Auswirkungen elektromagnetischer Felder auf die Melatoninproduktion beim Menschen, wobei naeher auf die Bedeutung des Melatonins beim Tag-Nacht-Rhythmus, dem Schlaf, auf das Immunsystem, als Hormonantagonist und bei Tumorentstehung und -wachstum diskutiert werden. In einem zweiten Teil diskutieren die Autoren moegliche Auswirkungen auf elektronische Implantate, v.a. auf Herzschrittmacher. (orig.)

  3. Orthodontic brackets in high field MR imaging: experimental evaluation of magnetic field interactions at 3.0 tesla; Kieferorthopaedische Brackets in der Hochfeld-Magnetresonanz-Tomographie: Experimentelle Beurteilung magnetischer Anziehungs- und Rotationskraefte bei 3 Tesla

    Energy Technology Data Exchange (ETDEWEB)

    Kemper, J.; Adam, G. [Klinik und Poliklinik fuer Diagnostische und Interventionelle Radiologie, Universitaetsklinikum Eppendorf, Hamburg (Germany); Klocke, A.; Kahl-Nieke, B. [Poliklinik fuer Kieferorthopaedie, Universitaetsklinikum Eppendorf, Hamburg (Germany)

    2005-12-15

    Purpose: To evaluate static magnetic field interactions for 32 commonly used orthodontic brackets in a 3.0 T magnetic resonance imaging (MRI) system. Materials and methods: 32 orthodontic brackets consisting of a steel alloy (n=27), a cobalt-chromium alloy (n=2), ceramic (n=1), ceramic with a steel slot (n=1), and titanium (n=1) from 13 different manufacturers were tested for magnetic field interactions in a static magnetic field at 3.0 T (Gyroscan Intera 3.0 T, Philips Medical Systems, Best, Netherlands). The magnetic deflection force F{sub Z} [mN] was evaluated by determining the deflection angle {beta}[ ] using the established deflection angle test according to the ASTM guidelines. The magnetic-field-induced rotational force F{sub rot} or torque was qualitatively determined using a 5-point grading scale (0: no torque; +4: very strong torque). Results: In 18 of the 32 brackets, the deflection angle {beta} was found to be > 45 and the translational force exceeded the gravitational force F{sub G} on the particular bracket (F{sub Z}: 1.2-45.7 mN). The translational force F{sub Z} was found to be up to 68.5 times greater than the gravitational force F{sub G} (F{sub Z}/F{sub G}: 1.4-68.5). The rotational force F{sub rot} was correspondingly high (+3/+4) for those brackets. For the remaining 14 objects, the deflection angles were < 45 and the torque measurements ranged from 0 to +2. The static magnetic field did not affect the titanium bracket and the ceramic bracket. No measurable translational and rotational forces were found. (orig.)

  4. Static and dynamic magnetic properties of CoPt{sub 3}. Nanoparticles in comparison with bulk matter; Statische und dynamische magnetische Eigenschaften von CoPt{sub 3}. Nanopartikel im Vergleich zum Volumenmaterial

    Energy Technology Data Exchange (ETDEWEB)

    Raeder, C.

    2006-09-22

    In this work the structural and magnetic characteristics of CoPt{sub 3}-particles are examined. In particular the determination of the g-factor is of interest as well as the damping behavior of the magnetization vector under influence of a microwave radiation. Moreover the magnetic anisotropy energy density of individual particles is covered by the presented thesis. The particles exist in the chemically disordered phase. They are monocrystalline and monodisperse with a mean diameter of d=4.04 nm and a width of the size distribution of {sigma}=0.15, as determined by transmission electron microscopy. Moreover the particles are embedded into a polymer with high dilution (0.08 vol%). To compare the results for the particles CoPt{sub 3} films and bulk-material are prepared and examined with the same procedure. X-ray diffraction (XRD) shows that all three sample systems are an alloy and do not appear as cobalt clusters embedded in platinum. The lattice constant of the particles is increased by 0.5% in comparison to the bulk material (a{sub NP}=0.388{+-}0.003 nm). The evaluation of the peak widths of the XRD experiments exhibit a crystalline size of 95.5{+-}6.5 nm of the films and 48.5{+-}6.5 nm of the bulk material. The evaluation of the relative intensities of (111)- and (200)-peaks points the fact that both the film and the particles preferentially grow in the (111)-direction. The films are polycrystalline in the film-plane. From magnetic resonance measurements the g-factor and the damping constant {alpha} is extracted. The measurement shows that both the g-factor (about 2%) and the damping-constant {alpha} (about 125%) is increased in comparison to the film, and/or bulk material. For the films M{sub eff} is determined from angle-dependent resonance-field measurements. From the temperature dependence of the resonance field the magnetic anisotropy is determined. Because of the fact that the measurements could be done only to a minimum of 50 K the value of the anisotropy-constant K{sub eff} is extrapolated to 2 K: Tt results in K{sub eff}(T=2 K)=7.5.10{sup 4} J/m{sup 3}. Measurement of the temperature dependence of the coercive field yields a value of K{sub eff}(T=2 K)=6.1.10{sup 4} J/m{sup 3}. With the same procedure one obtains K{sub eff}(T=2 K)=7.25.10{sup 4} J/m{sup 3} for a sample with a higher concentration (13 vol%). Both the particles and the bulk material are also examined by means of X-ray circular dichroism. With the help of the sum rules the element specific spin and orbital moments are determined and converted into the g-factor. (orig.)

  5. Study on the electronic calibration of the liquid-argon calorimeteand teh detection of invisbly decaying Higgs bosons in the ATLAS experiment; Studie zur elektronischen Kalibration der Fluessig-Argon-Kalorimeter und zur Entdeckung unsichtbar zerfallender Higgs-Bosonen im ATLAS-Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Schroff, D.

    2004-06-01

    At the LHC in Geneva the ATLAS experiment will start at 2007. The present work studies methods of the calibration of the liquid argon calorimeters and show the potential for the invisible decaying higgs-boson searches at the ATLAS experiment. Two calibration methods were studied and tested. Both fullfill the requirements for noise dependency and uniformity. In addition a test beam analysis were performed. The analysis of the invisible decaying higgs-boson were performed in the ttH and gluon-fusion channels. The gluon fusion channel is hopeless, but the ttH can contribute to the discovery potential. The results were combined with the VBF analysis and interpreted in the Phion-model and SUSY. (orig.)

  6. Devlopments of components for the detector driving system of the PANDA calorimeter and studies on the photoproduction of excited η mesons with the CB/ELSA experiment; Entwicklung von Komponenten fuer das Detektorsteuersystem des PANDA-Kalorimeters und Studien zur Photoproduktion angeregter η-Mesonen mit dem CB/ELSA-Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Triffterer, Tobias

    2016-01-28

    This PhD thesis (written in German language) consists of two parts: The first part describes developments for the Detector Control System of the electromagnetic calorimeter of the PANDA detector. An alarm and current border regulation system has been developed for this to ensure the correct functioning of the detector and to prevent damages. In addition, a database system (endcap production database) has been created to accompany the construction of the forward endcap and archive the characteristics of the photodetectors. The second part deals with the investigation into excited η mesons using the data measured with the CB/ELSA experiment. The distribution of the η' production angle in the decay channel η'→ ηπ{sup 0}π{sup 0} has been calculated for the first time within the beam photo energy range of 2500 to 2950 MeV. Furthermore, the relative effective cross section of the η(1405) to the η' could be determined to 0.16±0.05 (3.2σ). This shows evidence for a more complex nature of the η(1405).

  7. Influence of the surface topography, morphology and structure on magnetic properties of ion beam sputtered iron layers, Fe/Cr/Fe- and Fe/MgO/Fe multilayers; Untersuchung der Morphologie und magnetische Eigenschaften von ionenstrahl-gesputterten Eisen-Einzelschichten, Fe/Cr/Fe- und Fe/MgO/Fe-Schichtsystemen

    Energy Technology Data Exchange (ETDEWEB)

    Steeb, Alexandra

    2007-04-05

    In this PhD Thesis, the influence of the surface topography, morphology and structure on magnetic properties of ion beam sputtered iron layers on GaAs is examined. To analyze the structure of the produced iron films, low energy electron diffraction and scanning tunneling microscopy is employed. The utilized methods to investigate the magnetic properties are Kerr- and SQUID-magnetometry and ferromagnetic resonance. It is demonstrated that on untreated as well as on presputtered and heated GaAs substrates the sputtered iron films grow epitaxially. The least surface roughness of 1 A exhibit iron films grown on untreated GaAs, while iron films on heated GaAs have the highest roughness of 30 A. The largest crystal anisotropy constant is found for the presputtered GaAs/Fe-System. For this preparation method, two monolayers of iron are determined to be magnetically dead layers. At a film thickness of 100 A, 83% of the value for saturation magnetization of bulk iron are achieved. The small observed FMR-linewidths confirm the good bulk properties of the ion beam sputtered iron. Furthermore, an antiferromagnetic interlayer exchange coupling in sputtered Fe/Cr/Fe-films was achieved. For a thickness of 12 to 17 A of the chrome interlayer, a coupling strength up to 0.2 mJ/m{sup 2} is found. To account for the small coupling strength, a strong intermixing at the interface is assumed. Finally, epitaxial Fe/MgO/Fe/FeMn multilayers are deposited on GaAs. After the structuring, it is possible to detect tunneling processes in the tunneling contacts with current-voltage measurements. The tunnel magneto resistance values of 2% are small, which can be explained by the absence of sharp, well-defined interfaces between the Fe/FeMn and the Fe/MgO interfaces. These results demonstrate, that analog to MBE the ion beam sputtering method realizes good magnetic bulk properties. However, interface sensitive phenomena are weakened because of a strong intermixing at the interfaces. (orig.)

  8. Spin-polarized scanning tunneling microscopy of magnetic nanostructures at the example of bcc-Co/Fe(110), Fe/Mo(110), and copper phthalocyanine/Fe(1110); Spinpolarisierte Rastertunnelmikroskopie magnetischer Nanostrukturen am Beispiel von bcc-Co/Fe(110), Fe/Mo(110) und Kupfer-Phthalocyanin/Fe(110)

    Energy Technology Data Exchange (ETDEWEB)

    Methfessel, Torsten

    2010-12-09

    This thesis provides an introduction into the technique of spin-polarized scanning tunnelling microscopy and spectroscopy as an experimental method for the investigation of magnetic nanostructures. Experimental results for the spin polarized electronic structure depending on the crystal structure of ultrathin Co layers, and depending on the direction of the magnetization for ultrathin Fe layers are presented. High-resolution measurements show the position-dependent spin polarization on a single copper-phthalocyanine molecule deposited on a ferromagnetic surface. Co was deposited by molecular beam epitaxy on the (110) surface of the bodycentered cubic metals Cr and Fe. In contrast to previous reports in the literature only two layers of Co can be stabilized in the body-centered cubic (bcc) structure. The bcc-Co films on the Fe(110) surface show no signs of epitaxial distortions. Thicker layers reconstruct into a closed-packed structure (hcp / fcc). The bcc structure increases the spin-polarization of Co to P=62 % in comparison to hcp-Co (P=45 %). The temperature-dependent spin-reorientation of ultrathin Fe/Mo(110) films was investigated by spin-polarized spectroscopy. A reorientation of the magnetic easy axis from the [110] direction along the surface normal to the in-plane [001] axis is observed at T (13.2{+-}0.5) K. This process can be identified as a discontinuous reorientation transition, revealing two simultaneous minima of the free energy in a certain temperature range. The electronic structure of mono- and double-layer Fe/Mo(110) shows a variation with the reorientation of the magnetic easy axis and with the direction of the magnetization. The investigation of the spin-polarized charge transport through a copper-phthalocyanine molecule on the Fe/Mo(110) surface provides an essential contribution to the understanding of spin-transport at the interface between metal and organic molecule. Due to the interaction with the surface of the metal the HOMO-LUMO energy gap of the free molecule is filled with interface states. These states reduce the spin-polarization of the tunneling current through the molecule by an additional unpolarized current contribution, which leads to an energy-independent reduction of the spin-polarization by a factor of two. Spin-polarized interface states with larger distance from the Fermi-edge lead to further contributions to the effective spinpolarization that are different for ligands and center positions. These studies demonstrate the possibility of an efficient spin injection into organic semiconductors, and thus the potential of these materials for further development of spintronic devices. (orig.)

  9. Study of electronic excitation and diffraction effects as well as growth, structure, and magnetic properties of ultrathin 3d metal films on Cu(001) by means of grazing-incidence ion scattering; Untersuchung elektronischer Anregungs- und Beugungseffekte sowie Wachstum, Struktur und magnetischer Eigenschaften ultraduenner 3d-Metallfilme auf Cu(001) mittels streifender Ionenstreuung

    Energy Technology Data Exchange (ETDEWEB)

    Bernhard, T.

    2006-11-23

    H{sup +} and He{sup +} ions with an energy of 25 keV are scattered under a grazing angle of incidence from a clean and flat Cu(001) surface. For specific azimuthal orientations of the crystal surface with respect to low index directions in the surface plane we observe the ion induced emission of electrons with a conventional LEED (low energy electron diffraction) setup. By operating the instrument in an energy dispersive mode we find intensity distributions of emitted electrons which can unequivocally be ascribed to diffraction effects at the target surface. From this ion induced LEED-reflexes (IILEED) we get important information about the electron excitation- and emission effects during the scattering process. In the second part of this work we investigate the correlation between thin-film growth (Co,Fe,Mn on Cu(001)) and electron emission in the regime of grazing ion scattering. The ''rough'' surface of uncompleted layers increase the probability of binary collisions of incident ions with individual atoms at the surface. The energy spectras and the number distribution of emitted electrons are substantially influenced by these ''violent'' collisions and allow us to monitor growth of thin films via simple measurements of target current or from energy spectra of emitted electrons. The method provides excellent signals and is also applicable in the regime of poor layer growth. By making use of ion beam triangulation (IBT), direct information on the atomic structure of thin films and substrate surfaces is obtained. We discuss in the third part of this work a new variant of this method based on the detection of the number of emitted electrons. The data are analyzed via computer simulations using classical mechanics which provides a quantitative analysis with respect to projectile trajectories. This new detection scheme allows the determination of the in-plane structure of reconstructed thin films and surfaces with high precision. The impressed potential of this method is demonstrated by quantitative analysis of the structural phases of Fe and Mn on Cu(001). (orig.)

  10. Structural, magnetic, and lattice-dynamical interface properties of epitactical iron films on InAs(001) and GaAs(001) substrates; Strukturelle, magnetische und gitterdynamische Grenzflaecheneigenschaften von epitaktischen Eisenfilmen auf InAs(001)- und GaAs(001)-Substraten

    Energy Technology Data Exchange (ETDEWEB)

    Peters, Robert

    2009-07-14

    In this thesis the structure, magnetism and interface properties of ferromagnet-semiconductor hybrid structures were investigated. The main goal of this thesis was to obtain information on physical properties at the interface between a ferromagnetic metal and a III-V semiconductor (SC). For this purpose Fe films that serve as ferromagnetic contacts were deposited in ultrahigh vacuum (UHV) on InAs(001) and GaAs(001) substrates, respectively, and investigated. Both systems are interesting model systems with respect to electrical spin injection from a ferromagnetic metal into a semiconductor. In order for spin injection to occur, it is known that a Schottky barrier must form at the Fe/SC interface. Film growth and film structure were investigated in-situ in UHV by electron diffraction (RHEED) and ex-situ by X-ray diffraction. For determining the magnetic properties {sup 57}Fe conversion electron Moessbauer spectroscopy (CEMS) combines with {sup 57}Fe probe-layer technique was employed at different temperatures. Further, the partial Fe phonon density of states (PDOS) at the Fe/InAs (001) interface was determined by nuclear resonant inelastic X-ray scattering (NRIXS) from a {sup 57}Fe probe-layer. The CEM spectra (at room temperature) provided relatively high values of the average hyperfine magnetic field of left angle B{sub hf} right angle {proportional_to} 27 T and of the most-probable hyperfine magnetic field of B{sub hf,} {sub peak} {proportional_to} 30 T. This provides evidence for relativ high average Fe magnetic moments of {proportional_to} 1.8 {mu}{sub B}. The partial Fe phonon density of states (PDOS) at the Fe/InAs(001) interface is remarkably modified as compared to that of bulk bcc Fe. Using magnetometry and {sup 57}Fe CEMS, a strong temperature dependent magnetization directions was observed for Fe/Tb multilayers on InAs(001). Furthermore it is shown that such Fe/Tb multilayers on p-InAs(001) with perpendicular spin texture are useful as potential electrical contacts for spin injection at remanence (in zero field), because current-voltage behavior with typical diode characteristics was measured at low temperature, providing evidence for a Schottky barrier. With these samples at low temperature, electroluminescence in the infrared region at about 3 {mu}m was observed. Ultrathin Fe films of 2.5 monolayers coverage with an non-percolated island morphology were deposited on GaAs(001) and investigated in-situ in UHV by {sup 57}Fe CEMS with respect to their magnetic properties. Temperature dependent CEM spectra provide evidence for superparamagnetic behavior of these uncapped Fe islands, with a blocking temperature of T{sub B} {proportional_to}165 K. Moreover, the influence of different cap layers (Pt,Au) on the magnetic properties of the Fe islands was studied. (orig.)

  11. Toepassing van hoge-Tc supergeleiding in een 7-kanaals hartscanner

    NARCIS (Netherlands)

    Brake, ter Marcel

    1996-01-01

    Op de valreep van 1995 werd in de leerstoel Lage Temperaturen van de Universiteit Twente de laaste hand gelegd aan een 7-kanaals magnetometer, uitgerust met zogenaamde hoge-Tc SQUIDs In januari 1996 werden hiermee de eerste hartslagmetingen in een magnetisch afgeschermde kamer verricht en werden mag

  12. Ultrafast Laser Induced Magnetization Dynamics in High Magnetic Fields

    NARCIS (Netherlands)

    Becker, J.J.

    2016-01-01

    In dit proefschrift combineer ik hoge magneetvelden tot 37.5 T met ultrakorte laser pulsen in een unieke opstelling, om de magnetische eigenschappen van nanometer-dunne lagen te onderzoeken. Ik laat zien, dat femtoseconde laser pulsen gebruikt kunnen worden om magnetisme in materialen voor de

  13. Magnetocalorific materials for cooling at room temperature; Magnetocalorische materialen voor koeltoepassingen bij kamertemperatuur

    Energy Technology Data Exchange (ETDEWEB)

    Brueck, E.; Dung, N.H.; Ou, Z.Q.; Caron, L.; Zhang, L.; Buschow, K.H.J. [Fundamental Aspects of Materials and Energy, Faculty of Applied Sciences, Delft University of Technology, Delft (Netherlands)

    2013-09-01

    The thermodynamics of magnetic cooling is briefly discussed. In addition, some examples are given of prototypes and attention is paid to new transition metal-based magnetocaloric materials. Such materials are currently being developed and can lead to competitive commercial heat pumps [Dutch] De thermodynamica van magnetische koeling wordt kort besproken. Daarnaast worden enkele voorbeelden gegeven van prototypes en wordt aandacht besteed aan nieuwe op transitiemetaal gebaseerde magnetocalorische materialen. Dergelijke materialen worden momenteel ontwikkeld en kunnen leiden tot commercieel concurrerende warmtepompen.

  14. Magnetic vortices in gauge/gravity duality

    OpenAIRE

    Strydom, Migael

    2014-01-01

    Wir untersuchen stark gekoppelte Phänomene unter Verwendung der Dualität zwischen Eich- und Gravitationstheorien. Dabei liegt ein besonderer Fokus einerseits auf Vortex Lösungen, die von einem magnetischem Feld verursacht werden, und andererseits auf zeitabhängigen Problemen in holographischen Modellen. Das wichtigste Ergebnis ist die Entdeckung eines unerwarteten Effektes in einem einfachen holografischen Modell: ein starkes nicht abelsches magnetisches Feld verursach...

  15. Electrical engineering. Basic knowledge. 2. ed.; Elektrotechnik. Allgemeine Grundbildung

    Energy Technology Data Exchange (ETDEWEB)

    Frielingsdorf, H.; Lintermann, F.J.

    2001-07-01

    The textbook provides information on the following subjects: Fundamentals of electric circuits, connection of electric resistors, technical circuits, electric fields and condensers, magnetic fields and coils, fundamentals of a.c. engineering, dangerous body currents, fundamentals of electronical and control engineering. [German] Lehrbuch mit folgendem Inhalt: Grundbegriffe des elektrischen Stromkreises, Zusammenschaltung elektrischer Widerstaende, technischer Stromkreis, elektrisches Feld und Kondensator, magnetisches Feld und Spule, Grundlagen der Wechselstromtechnik, gefaehrliche Koerperstroeme, Grundlagen der Elektronik und Steuerungstechnik.(GL)

  16. Weitere Detektorarten

    Science.gov (United States)

    Krieger, Hanno

    In diesem Kapitel werden weitere für die Dosimetrie und die Strahlungsmessung wichtige Detektorprinzipien dargestellt. Neben den chemischen Detektoren, die auf dem Auslösen einer makroskopisch nachweisbaren chemischen Reaktion beruhen, wird die Filmemulsion, ein bis heute wichtiger Detektor der Dosimetrie und der bildgebenden Radiologie, detailliert beschrieben. Die anschließend dargestellten Kalorimeter werden zunehmend als Primärnormalstandard für die Dosimetrie eingesetzt. Die für die Strahlungsmessung weniger bedeutenden Nachweisverfahren wie Elektronenspinresonanz, die Exoelektronenemission und das Lyolumineszenzverfahren werden nur kurz erläutert.

  17. Development of a new metal casting technique for micromechanical systems; Entwicklung einer neuen Metallgiesstechnik fuer die Mikromechanik

    Energy Technology Data Exchange (ETDEWEB)

    Bach, F.W.; Moehwald, K.; Hollaender, U.; Nakhosteen, B. [Dortmund Univ. (Germany). Lehrstuhl fuer Werkstofftechnologie

    2001-03-01

    The effect that metallic molten masses can flow into deep and narrow gaps by capillary action forms the basis of the mould filling mechanism of the micro casting process presented here. Potential applications of ''Capillary Action Microcasting'' are the minimal invasive surgery (e. g. micromechanical endoscope items, grippers and cutting tools), magnetic actuators and the micro-electromechanical system (MEMS) technique (e. g. magnetic cores for micromechanical drive components and sensors) as well as the technology of mechanism design. Castings of a eutectic silver-copper alloy prove that both a definition and a guaranteed withdrawal of the cast part are achieved. The procedure is suitable and promising for the production of magnetic components, e. g. Fe47Sb53 for micro-electric motors. (orig.) [German] Der Effekt, dass metallische Schmelzen durch Kapillardruck in enge, tiefe Spalte einfliessen koennen, bildet die Basis fuer den Formfuellungsmechanismus des hier vorgestellten Mikro-Giessverfahrens, des ''Metall-Kapillardruckgiessens''. Potentielle Anwendungen werden in der minimalinvasiven Chirurgie (z. B. mikromechanische Endoskopelemente, Greiferzangen und Schneidwerkzeuge), der Magnetoaktorik und der mikro-elektromechanischen System (MEMS)-Technik, z. B. magnetische Kerne fuer mikromechanische Antriebselemente und Sensoren, sowie der Getriebetechnik erwartet. Abguesse, die mit Ag72Cu28-Schmelzen kapillardruckgegossen wurden, belegen, dass sowohl eine hohe Konturentreue als auch eine sichergestellte Entnahme des Gussteils realisiert wird. Das Verfahren ist geeignet und aussichtsreich fuer die Herstellung magnetischer Bauteile aus Fe47Sb53, wie z. B. fuer Mikro-Elektromotoren. (orig.)

  18. Design and specifications of the diagnostics for the instrumented calorimeter of source for the production of ions of deuterium extracted from radio frequency plasma.

    Science.gov (United States)

    De Muri, M; Dalla Palma, M; Fasolo, D; Pasqualotto, R; Pomaro, N; Rizzolo, A; Serianni, G; Tollin, M

    2012-02-01

    In the development of the neutral beam injector for ITER experiment, the test facility SPIDER is going to be built. To measure the beam parameters, several diagnostics are used. One of them is the Short-Time Retractable Instrumented Kalorimeter Experiment (STRIKE) which measures beam uniformity, beamlet divergence, and stripping losses. This contribution gives an overview of the diagnostics dedicated to these measurements: thermal cameras, thermocouples, current sensors, and electrostatic sensors. The specifications of these diagnostics have been defined according to the results of electrostatic and thermal simulations. A failure modes and effects analysis has been performed during the design. Consequently the project of the STRIKE diagnostics has been optimized to reduce the possible failure risks.

  19. Thermal and electrostatic simulations of the diagnostic calorimeter for the source for production of ion of deuterium extracted from RF plasma beam.

    Science.gov (United States)

    Serianni, G; Dalla Palma, M; De Muri, M; Fasolo, D; Pasqualotto, R; Pomaro, N; Rizzolo, A; Tollin, M

    2012-02-01

    To study and optimise negative ion production for the ITER neutral beam injectors, a test facility is under construction in Padova with the aim of testing beam characteristics and to verify the source proper operation. The instrumented calorimeter STRIKE (short-time retractable instrumented kalorimeter experiment) is being developed to characterise the SPIDER (Source for Production of Ion of Deuterium Extracted from RF plasma) beam during short operations. The paper presents an investigation of the response of STRIKE measurement systems. It results that biasing is necessary to cope with the influence of secondary electrons on current measurements; moreover, despite the discretisation of the recorded thermal patterns introduced by the pixels of thermal cameras, a sufficient spatial resolution is expected.

  20. Fundamentals of electrical engineering; 5. tot. new rev. ed.; Grundlagen der Elektrotechnik

    Energy Technology Data Exchange (ETDEWEB)

    Pregla, R. [Fernuniversitaet (Gesamthochschule) Hagen (Germany). Fachbereich Elektrotechnik

    1998-10-01

    This is a textbook for the first two university terms in electrical engineering. Subjects: Description of physical processes; Static electric fields; Electric current; d.c. circuits; Calculation of linear networks; Magnetic fields; Electromagnetic induction; Electric circuits in the quasi-stationary state; Alternating currents and networks. To facilitate self-studies, the book is divided into 14 training lessons. (orig.) [Deutsch] Dieser Band enthaelt - analog zur Stoffvermittlung in den ersten beiden Studiensemestern - folgende inhaltliche Schwerpunkte: - Beschreibung physikalischer Vorgaenge - statisches elektrisches Feld - elektrischer Strom - Gleichstromschaltungen - Berechnung linearer Netzwerke - magnetisches Feld - elektromagentische Induktion - elektrischer Stromkreis im quasistationaeren Zustand - Wechselstroeme und Netzwerke. Fuer die autodidaktische Erarbeitung des Stoffes besonders vorteilhaft ist die Aufteilung der Inhalte in 14 Kurseinheiten, die jeweils mit einer Vororientierung beginnen. (orig./GL)

  1. Electromagnetic converters and sensors. Fundamentals, fieldnumerical calculation of electromagnetic fields and application in mechatronics. 2. new rev. and enl. ed.; Elektromagnetische Wandler und Sensoren. Grundlagen, feldnumerische Berechnung elektromagnetischer Felder und Anwendungen in der Mechatronik

    Energy Technology Data Exchange (ETDEWEB)

    Cassing, W.; Stanek, W.; Erd, L.; Huebner, K.D.; Koch, J.; Dukart, A.

    2002-07-01

    Electrodynamic theories and calculation methods are discussed with particular regard to permanent electromagnetic circuits in mechatronics. Design strategies and computer calculation methods are explained by examples and applied to magnetic sensors, e.g. in automotive, electrically switched permanent magnet systems and actuators. The theoretical background is based primarily on the complete Maxwell's equations with their interdisciplinary related fields and up to compact formulations for use in relativistic quantum electrodynamics. [German] In diesem Fachbuch werden elektrodynamische Theorien und verschiedene Berechnungsverfahren unter besonderer Beruecksichtigung dauerelektromagnetischer Kreise in der Mechatronik behandelt. An ausgewaehlten Berechnungsbeispielen werden die wichtigsten Entwurfsstrategien und computerorientierten Rechenverfahren erlaeutert und auf magnetische Sensoren u.a. aus dem Bereich Automotive, elektrisch schaltbare Dauermagnetsysteme und Aktuatoren angewendet. Der theoretische Hintergrund hierfuer sind vorrangig die kompletten Maxwell'schen Gleichungen mit interdisziplinaeren Nachbargebieten bis hin zu kompakten Formulierungen fuer die relativistische Quantenelektrodynamik. (orig.)

  2. Remain stable.; Schoen stabil bleiben.

    Energy Technology Data Exchange (ETDEWEB)

    Teroerde, Michael; Schulz, Detlef [Helmut-Schmidt-Univ., Hamburg (Germany). Professur fuer Elektrische Energiesysteme; Eckoldt, Hans-Joerg [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Fachgebiet Magnetstromversorgung

    2013-11-15

    In the German power grid the increasing photovoltaic power plants and wind turbines provide due to their volatile energy supply high demands on the control of the power grid. In the case of malfunctions in the network short-term energy storage could participate in the grid control. Superconducting magnetic energy storage (SMES) belongs to the efficient short-term energy storage. A SMES system was investigated at DESY in Hamburg. [German] Im deutschen Stromnetz stellen die zunehmenden Photovoltaik- und Windkraftanlagen aufgrund ihrer stark schwankenden Energieeinspeisung hohe Anforderungen an die Regelung des Stromnetzes. Bei eventuell auftretenden Stoerungen im Netz koennten Kurzzeitenergiespeicher an der Netzregelung teilnehmen. Zu den effizienten Kurzzeitspeichern gehoeren supraleitende magnetische Energiespeicher (SMES). Ein SMES-System wurde bei DESY in Hamburg untersucht.

  3. Preliminary results concerning the simulation of beam profiles from extracted ion current distributions for mini-STRIKE

    Energy Technology Data Exchange (ETDEWEB)

    Agostinetti, P., E-mail: piero.agostinetti@igi.cnr.it; Serianni, G.; Veltri, P. [Consorzio RFX (CNR, ENEA, INFN, Università di Padova, Acciaierie Venete SpA), Corso Stati Uniti 4, 35127 Padova (Italy); Giacomin, M. [Physics Department, Università di Padova, via F. Marzolo 8, 35131 Padova (Italy); Bonomo, F.; Schiesko, L. [Max-Planck-Institut für Plasmaphysik, Boltzmannstrasse 2, D-85748 Garching (Germany)

    2016-02-15

    The Radio Frequency (RF) negative hydrogen ion source prototype has been chosen for the ITER neutral beam injectors due to its optimal performances and easier maintenance demonstrated at Max-Planck-Institut für Plasmaphysik, Garching in hydrogen and deuterium. One of the key information to better understand the operating behavior of the RF ion sources is the extracted negative ion current density distribution. This distribution—influenced by several factors like source geometry, particle drifts inside the source, cesium distribution, and layout of cesium ovens—is not straightforward to be evaluated. The main outcome of the present contribution is the development of a minimization method to estimate the extracted current distribution using the footprint of the beam recorded with mini-STRIKE (Short-Time Retractable Instrumented Kalorimeter). To accomplish this, a series of four computational models have been set up, where the output of a model is the input of the following one. These models compute the optics of the ion beam, evaluate the distribution of the heat deposited on the mini-STRIKE diagnostic calorimeter, and finally give an estimate of the temperature distribution on the back of mini-STRIKE. Several iterations with different extracted current profiles are necessary to give an estimate of the profile most compatible with the experimental data. A first test of the application of the method to the BAvarian Test Machine for Negative ions beam is given.

  4. High energy flux thermo-mechanical test of 1D-carbon-carbon fibre composite prototypes for the SPIDER diagnostic calorimeter

    Science.gov (United States)

    De Muri, M.; Cavallin, T.; Pasqualotto, R.; Dalla Palma, M.; Cervaro, V.; Fasolo, D.; Franchin, L.; Tollin, M.; Greuner, H.; Böswirth, B.; Serianni, G.

    2014-02-01

    Operation of the thermonuclear fusion experiment ITER requires additional heating via injection of neutral beams from accelerated negative ions. In the SPIDER test facility, under construction in Padova, the production of negative ions will be studied and optimised. STRIKE (Short-Time Retractable Instrumented Kalorimeter Experiment) is a diagnostic used to characterise the SPIDER beam during short pulse operation (several seconds) to verify if the beam meets the ITER requirements about the maximum allowed beam non-uniformity (below ±10%). The major components of STRIKE are 16 1D-CFC (Carbon-Carbon Fibre Composite) tiles, observed at the rear side by a thermal camera. This contribution gives an overview of some tests under high energy particle flux, aimed at verifying the thermo-mechanical behaviour of several CFC prototype tiles. The tests were performed in the GLADIS facility at IPP (Max-Plank-Institut für Plasmaphysik), Garching. Dedicated linear and nonlinear simulations were carried out to interpret the experiments and a comparison of the experimental data with the simulation results is presented. The results of some morphological and structural studies on the material after exposure to the GLADIS beam are also given.

  5. High energy flux thermo-mechanical test of 1D-carbon-carbon fibre composite prototypes for the SPIDER diagnostic calorimeter

    Energy Technology Data Exchange (ETDEWEB)

    De Muri, M., E-mail: michela.demuri@igi.cnr.it; Pasqualotto, R.; Dalla Palma, M.; Cervaro, V.; Fasolo, D.; Franchin, L.; Tollin, M.; Serianni, G. [Consorzio RFX, Euratom-ENEA association, Corso Stati Uniti 4, 35127 Padova (Italy); Cavallin, T. [Istituto per l’Energetica e le Interfasi, Corso Stati Uniti 4, 35127 Padova (Italy); Greuner, H.; Böswirth, B. [Max-Planck-Institut für Plasmaphysik, D-85748 Garching bei München (Germany)

    2014-02-15

    Operation of the thermonuclear fusion experiment ITER requires additional heating via injection of neutral beams from accelerated negative ions. In the SPIDER test facility, under construction in Padova, the production of negative ions will be studied and optimised. STRIKE (Short-Time Retractable Instrumented Kalorimeter Experiment) is a diagnostic used to characterise the SPIDER beam during short pulse operation (several seconds) to verify if the beam meets the ITER requirements about the maximum allowed beam non-uniformity (below ±10%). The major components of STRIKE are 16 1D-CFC (Carbon-Carbon Fibre Composite) tiles, observed at the rear side by a thermal camera. This contribution gives an overview of some tests under high energy particle flux, aimed at verifying the thermo-mechanical behaviour of several CFC prototype tiles. The tests were performed in the GLADIS facility at IPP (Max-Plank-Institut für Plasmaphysik), Garching. Dedicated linear and nonlinear simulations were carried out to interpret the experiments and a comparison of the experimental data with the simulation results is presented. The results of some morphological and structural studies on the material after exposure to the GLADIS beam are also given.

  6. Characterization, test and interpretative simulations of one-dimensional Carbon Fiber Composite prototype for SPIDER experiment

    Energy Technology Data Exchange (ETDEWEB)

    De Muri, M., E-mail: michela.demuri@igi.cnr.it [Consorzio RFX – Associazione Euratom-Enea sulla Fusione, corso Stati Uniti 4, I-35127 Padova (Italy); Dipartimento di Ingegneria Elettrica, Padova University, Padova (Italy); Cervaro, V.; Dal Bello, S.; Dalla Palma, M.; Fasolo, D.; Franchin, L.; Pasqualotto, R.; Pomaro, N.; Rizzolo, A.; Tollin, M.; Serianni, G. [Consorzio RFX – Associazione Euratom-Enea sulla Fusione, corso Stati Uniti 4, I-35127 Padova (Italy)

    2013-10-15

    Highlights: • Prototype ITER neutral beam injector to study the beam source behavior requires beam characterization. • Among several types of diagnostic, a calorimeter made of fiber carbon composite (CFC) tiles will be used. • The CFC thermal behaviour is study by laser beam and will be characterize in particel beam. • Experiments and simulations results are discussed. • Designs for tests in particle beams are presented. -- Abstract: For ITER operations, additional heating systems are required. One of these systems is the neutral beam injector (NBI). The SPIDER experiment, a small-scale NBI, is going to be built with the aim to optimize the beam source. For this reason it is provided with several diagnostics, among which the Short-Time Retractable Instrumented Kalorimeter Experiment (STRIKE). In this contribution, a characterization of the Carbon Fiber Composite (CFC) tiles, which are the main component of the diagnostic, is presented. Such analyses include tests with a power laser, exposure to particle beams and thermal stress tests. The results are discussed, which will drive the definition of the acceptance tests of the final supply of CFC tiles.

  7. Blower/air cooler with internally finned tubes; Ventilator-Luftkuehler mit innenberippten Rohren

    Energy Technology Data Exchange (ETDEWEB)

    Arnemann, M. [FKU - Forschungszentrum fuer Kaelte- und Umwelttechnik, Berlin (Germany)

    1997-12-31

    Heat transfer is higher in finned tubes than in smooth tubes. In order to assess the extent of improvement, internal heat tranfer coefficients and pressure losses of smooth and finned tubes were investigated on behalf of Walter Roller GmbH and Co. Two blower-type air coolers of identical design (except for the tubes) were investigated in a calorimeter using R22 and different refrigerant mass flows, evaporation temperatures and air temperatures. The results are the basis for new develoments by Walter Roller. Energetic assessment of the new type of evaporator was made on the basis of the DIN 8955 and ENV 328 standards. The results and findings are presented. (orig.) [Deutsch] Der Einsatz von innenberippten Rohren laesst im Vergleich mit glatten Rohren einen deutlich verbesserten inneren Waermeuebergang erwarten. Zur Abschaetzung der Groessenordnung dieser Verbesserungen wurden im Auftrag der Firma Walter Roller GmbH and Co. die inneren Waermeuebergangskoeffizienten und die Druckverluste von glatten und innenberippten Rohren experimentell bestimmt. Dazu wurden zwei bis auf die Rohre baugleiche Ventilator-Luftkuehler ineinem Kalorimeter untersucht. Mit dem Kaeltemittel R22 wurden fuer verschiedene Kaeltemittelmassenstroeme, Verdampfungstemperaturen und Lufttemperaturen die Kennzahlen bestimmt, die zur Charakterisierung der Rohre dienlich sind. Die Ergebnisse bildeten die Grundlage fuer eine Neuentwicklung im Hause Walter Roller. Die energetische Bewertung des neuen Verdampfertyps erfolgte in Anlehnung an die Normen DIN 8955 bzw. ENV 328. Die Untersuchungen und die Ergebnisse werden praesentiert. (orig.)

  8. High energy flux thermo-mechanical test of 1D-carbon-carbon fibre composite prototypes for the SPIDER diagnostic calorimeter.

    Science.gov (United States)

    De Muri, M; Cavallin, T; Pasqualotto, R; Dalla Palma, M; Cervaro, V; Fasolo, D; Franchin, L; Tollin, M; Greuner, H; Böswirth, B; Serianni, G

    2014-02-01

    Operation of the thermonuclear fusion experiment ITER requires additional heating via injection of neutral beams from accelerated negative ions. In the SPIDER test facility, under construction in Padova, the production of negative ions will be studied and optimised. STRIKE (Short-Time Retractable Instrumented Kalorimeter Experiment) is a diagnostic used to characterise the SPIDER beam during short pulse operation (several seconds) to verify if the beam meets the ITER requirements about the maximum allowed beam non-uniformity (below ±10%). The major components of STRIKE are 16 1D-CFC (Carbon-Carbon Fibre Composite) tiles, observed at the rear side by a thermal camera. This contribution gives an overview of some tests under high energy particle flux, aimed at verifying the thermo-mechanical behaviour of several CFC prototype tiles. The tests were performed in the GLADIS facility at IPP (Max-Plank-Institut für Plasmaphysik), Garching. Dedicated linear and nonlinear simulations were carried out to interpret the experiments and a comparison of the experimental data with the simulation results is presented. The results of some morphological and structural studies on the material after exposure to the GLADIS beam are also given.

  9. Tellurium rings as electron pair donors in cluster compounds and coordination polymers; Tellurringe als Elektronenpaardonoren in Clusterverbindungen und Koordinationspolymeren

    Energy Technology Data Exchange (ETDEWEB)

    Guenther, Anja

    2011-11-08

    In this dissertation novel and already known molecular tellurium rings are presented in cluster compounds and quasi-one-dimensional coordination polymers. The cyclic, homonuclear units are always stabilized by coordination to electron-rich transition metal atoms, with the coordinating tellurium atoms acting as two-electron donors. As a synthesis route, the solid-state reaction in quartz glass vials was used uniformly. In addition to structural determination, the focus was on the characterization of the resulting compounds. For this purpose, resistance measurements were carried out on selected compounds, the magnetic behavior and the thermal degradation reactions were investigated and accompanying quantum chemical calculations were carried out. [German] In dieser Dissertation werden neuartige sowie bereits bekannte molekulare Tellurringe in Clusterverbindungen und quasi-eindimensionalen Koordinationspolymeren vorgestellt. Die Stabilisierung der zyklischen, homonuklearen Einheiten erfolgt dabei stets durch die Koordination an elektronenreiche Uebergangsmetallatome, wobei die koordinierenden Telluratome gegenueber diesen als Zwei-Elektronendonoren fungieren. Als Syntheseroute wurde dabei einheitlich auf die Festkoerperreaktion in Quarzglasampullen zurueckgegriffen. Neben der Strukturaufklaerung stand die Charakterisierung der erhaltenden Verbindungen im Fokus der Arbeit. Dazu wurden an ausgewaehlten Verbindungen Widerstandsmessungen durchgefuehrt, das magnetische Verhalten sowie die thermischen Abbaureaktionen untersucht und begleitende quantenchemische Rechnungen durchgefuehrt.

  10. Electrosmog. Health hazards, limiting values, consumer protection; 3. ed.; Elektrosmog. Gesundheitsrisiken, Grenzwerte, Verbraucherschutz

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-12-31

    The book starts with the physical facts. All definitions and units required for understanding electrosmog are presented and discussed with a view to their practical application. The main part of the book is dedicated to the health hazards of elctrosmog. The present state of knowledge is outlined. Current limiting values are discussed along with their conceptional and political basis. The last part of the book discusses problems of consumber protection. It is shown how everybody can reduce their own exposure to electric and magnetic fields. (orig./MG) [Deutsch] Das Buch beginnt mit den physikalischen Fakten. Alle Begriffe und Einheiten, die zum Verstaendnis von Elektrosmog notwendig sind, werden vorgestellt und in Bezug zur Praxis gebracht. Den weitaus groessten Teil des Buches nehmen die gesundheitlichen Auswirkungen von Elektrosmog ein. Praesentiert wird der aktuelle wissenschaftliche Forschungsstand. Im Kapitel Grenzwerte, diskutiert werden die gueltigen Grenzwerte und ihre konzeptionelle und politische Basis. Der letzte Teil des Buches ist dem Verbraucherschutz gewidmet. Es wird gezeigt, wie man die eigene Belastung durch elektrische und magnetische Felder reduzieren kann. (orig./MG)

  11. Electrosmog. Effects of electromagnetic fields on human health. Report as of June 1993; Elektrosmog. Auswirkungen von elektromagnetischen Feldern auf den Menschen. Stand: Juni 1993

    Energy Technology Data Exchange (ETDEWEB)

    Brueggemeyer, H. [Niedersaechsisches Landesamt fuer Oekologie, Hildesheim (Germany)

    1993-06-01

    The brochure wants to inform on the current state of knowledge concerning this complex of subjects. An analysis of the available literature and many talks with scientists and persons directly concerned have shown the following: at present it cannot be excluded that electric, magnetic and electromagnetic fields, even of the field strengths encountered in every-day life, may constitute a certain nuisance or health hazard. The effect that these fields have on children and adolescents is particularly often referred to. In the author`s opinion, many instances call for further careful observation of this area. (orig./MG) [Deutsch] Die vorliegende Broschuere soll einen Ueberblick ueber den gegenwaertigen Stand der Kenntnis zu diesem Themenkomplex geben. Die Auswertung der vorliegenden Literatur und viele Gespraeche mit Wissenschaftlern und Betroffenen haben gezeigt, dass zur Zeit nicht ausgeschlossen werden kann, dass elektrische, magnetische und elektromagnetische Felder auch schon bei Feldstaerken, wie sie im Alltag vorkommen koennen, eine bestimmte Belaestigung oder ein Gesundheitsrisiko darstellen. Dabei wird immer wieder besonders auf die Wirkung auf Kinder und Heranwachsende abgehoben. (orig./MG)

  12. Test of 1D carbon-carbon composite prototype tiles for the SPIDER diagnostic calorimeter

    Science.gov (United States)

    Serianni, G.; Pimazzoni, A.; Canton, A.; Palma, M. Dalla; Delogu, R.; Fasolo, D.; Franchin, L.; Pasqualotto, R.; Tollin, M.

    2017-08-01

    Additional heating will be provided to the thermonuclear fusion experiment ITER by injection of neutral beams from accelerated negative ions. In the SPIDER test facility, under construction at Consorzio RFX in Padova (Italy), the production of negative ions will be studied and optimised. To this purpose the STRIKE (Short-Time Retractable Instrumented Kalorimeter Experiment) diagnostic will be used to characterise the SPIDER beam during short operation (several seconds) and to verify if the beam meets the ITER requirement regarding the maximum allowed beam non-uniformity (below ±10%). The most important measurements performed by STRIKE are beam uniformity, beamlet divergence and stripping losses. The major components of STRIKE are 16 1D-CFC (Carbon matrix-Carbon Fibre reinforced Composite) tiles, observed at the rear side by a thermal camera. The requirements of the 1D CFC material include a large thermal conductivity along the tile thickness (at least 10 times larger than in the other directions); low specific heat and density; uniform parameters over the tile surface; capability to withstand localised heat loads resulting in steep temperature gradients. So 1D CFC is a very anisotropic and delicate material, not commercially available, and prototypes are being specifically realised. This contribution gives an overview of the tests performed on the CFC prototype tiles, aimed at verifying their thermal behaviour. The spatial uniformity of the parameters and the ratio between the thermal conductivities are assessed by means of a power laser at Consorzio RFX. Dedicated linear and non-linear simulations are carried out to interpret the experiments and to estimate the thermal conductivities; these simulations are described and a comparison of the experimental data with the simulation results is presented.

  13. Alexander von Humboldt und Carl Friedrich Gauß als Wegbereiter der neuen Disziplin Erdmagnetismus

    Directory of Open Access Journals (Sweden)

    Karin Reich

    2011-03-01

    Full Text Available AbstractThough Alexander von Humboldt was motivated for the first time to deal with earthmagnetism during his stay in Freiberg, it was in France that he really became a specialist in this respect. During most of his journeys he made earthmagnetic measurements. His collaboration with Arago was of great importance, it was in Paris that the first magnetic observatory was built. Humboldt rendered outstanding services to the investigation of earth magnetism by two major achievements: 1. He emphasized intensity measurements and 2. he put forward the law that the magnetic intensity is increasing from the magnetic equator toward the magnetic poles. At least since 1803 Carl Friedrich Gauss was interested in earthmagnetism and especially in Humboldt’s early published data. That Wilhelm Weber became professor of physics at the University of Göttingen in 1831 was a turning point for Gauss. In 1833 Göttingen was the centre of investigating earthmagnetism, a new era began which lasted only until 1843. Gauss’ main contributions were more or less theoretical, in 1832/3 he transformed Humboldt’s relative intensity measurements into absolute ones which were independent of the instrument’s needle. A new epoch began with Gauss’ publication „Allgemeine Theorie des Erdmagnetismus” (1839. The main point was the newly defined notion of „potential“. Gauss was the first to present the surface of the earth with equipotential lines. ZusammenfassungAlexander von Humboldt hatte sich bereits in Freiberg mit dem Erdmagnetismus beschäftigt; jedoch erst in Frankreich lernte er die entsprechenden Beobachtungsmethoden kennen. Auf allen seinen Reisen machte er erdmagnetische Messungen. Seine Zusammenarbeit mit Arago in Paris war besonders fruchtbar, hier wurde das erste magnetische Observatorium gebaut. Humboldt beschäftigte sich vor allem mit Intensitätsmessungen; sein wichtigster Beitrag war die Feststellung, dass die magnetische Intensität vom

  14. Calibration of historical geomagnetic observations from Prague-Klementinum

    Science.gov (United States)

    Hejda, Pavel

    2015-04-01

    The long tradition of geomagnetic observations on the Czech territory dates back to 1839, when regular observations were started by Karl Kreil at the Astronomical Observatory Prague-Klementinum. Observations were carried out manually, at the beginning more than ten times per day and the frequency later decreased to 5 daily observations. Around the turn of century the observations became to be disturbed by the increasing urban magnetic noise and the observatory was closed down in 1926. The variation measurements were completed by absolute measurements carried out several times per year. Thanks to the diligence and carefulness of Karl Kreil and his followers all results were printed in the yearbooks Magnetische und meteorologische Beobachtungen zu Prag and have thus been saved until presence. The entire collection is kept at the Central Library of the Czech Academy of Sciences. As the oldest geomagnetic data have been recently recognized as an important source of information for Space Weather studies, digitization and analysis of the data have been now started. Although all volumes have been scanned with the OCR option, the low quality of original books does not allow for an automatic transformation to digital form. The data were typed by hand to Excel files with a primary check and further processed. Variation data from 1839 to 1871 were published in measured units (scales of divisions). Their reduction to physical units was not as straight forward as we are used in recent observatories. There were several reasons: (i) the large heavy magnetic rods were not as stable as recent systems, (ii) the absolute measurements of horizontal components were carried out by the genius but rather complicated Gauss method, (iii) the intervals between absolute measurements was on the scale of months and eventual errors were not recognized timely. The presentation will discuss several methods and give examples how to cope with the problem.

  15. Animal Magnetism, Psychiatry and Subjective Experience in Nineteenth-Century Germany: Friedrich Krauß and his Nothschrei.

    Science.gov (United States)

    Brückner, Burkhart

    2016-01-01

    Friedrich Krauß (1791-1868) is the author of Nothschrei eines Magnetisch-Vergifteten [Cry of Distress by a Victim of Magnetic Poisoning] (1852), which has been considered one of the most comprehensive self-narratives of madness published in the German language. In this 1018-page work Krauß documents his acute fears of 'mesmerist' influence and persecution, his detainment in an Antwerp asylum and his encounter with various illustrious physicians across Europe. Though in many ways comparable to other prominent nineteenth-century first-person accounts (eg. John Thomas Perceval's 1838 Narrative of the Treatment Experienced by a Gentleman or Daniel Paul Schreber's 1903 Memoirs of my Nervous Illness), Krauß's story has received comparatively little scholarly attention. This is especially the case in the English-speaking world. In this article I reconstruct Krauß's biography by emphasising his relationship with physicians and his under-explored stay at the asylum. I then investigate the ways in which Krauß appropriated nascent theories about 'animal magnetism' to cope with his disturbing experiences. Finally, I address Krauß's recently discovered calligraphic oeuvre, which bears traces of his typical fears all the while showcasing his artistic skills. By moving away from the predominantly clinical perspective that has characterised earlier studies, this article reveals how Friedrich Krauß sought to make sense of his experience by selectively appropriating both orthodox and non-orthodox forms of medical knowledge. In so doing, it highlights the mutual interaction of discourses 'from above' and 'from below' as well as the influence of broader cultural forces on conceptions of self and illness during that seminal period.

  16. Animal Magnetism, Psychiatry and Subjective Experience in Nineteenth-Century Germany: Friedrich Krauß and his Nothschrei

    Science.gov (United States)

    Brückner, Burkhart

    2016-01-01

    Friedrich Krauß (1791–1868) is the author of Nothschrei eines Magnetisch-Vergifteten [Cry of Distress by a Victim of Magnetic Poisoning] (1852), which has been considered one of the most comprehensive self-narratives of madness published in the German language. In this 1018-page work Krauß documents his acute fears of ‘mesmerist’ influence and persecution, his detainment in an Antwerp asylum and his encounter with various illustrious physicians across Europe. Though in many ways comparable to other prominent nineteenth-century first-person accounts (eg. John Thomas Perceval’s 1838 Narrative of the Treatment Experienced by a Gentleman or Daniel Paul Schreber’s 1903 Memoirs of my Nervous Illness), Krauß’s story has received comparatively little scholarly attention. This is especially the case in the English-speaking world. In this article I reconstruct Krauß’s biography by emphasising his relationship with physicians and his under-explored stay at the asylum. I then investigate the ways in which Krauß appropriated nascent theories about ‘animal magnetism’ to cope with his disturbing experiences. Finally, I address Krauß’s recently discovered calligraphic oeuvre, which bears traces of his typical fears all the while showcasing his artistic skills. By moving away from the predominantly clinical perspective that has characterised earlier studies, this article reveals how Friedrich Krauß sought to make sense of his experience by selectively appropriating both orthodox and non-orthodox forms of medical knowledge. In so doing, it highlights the mutual interaction of discourses ‘from above’ and ‘from below’ as well as the influence of broader cultural forces on conceptions of self and illness during that seminal period. PMID:26651186

  17. On the differential properties of internal magnetic field models at the Earth's surface and at satellite altitudes

    Science.gov (United States)

    Webers, Wigor A.

    2007-03-01

    The inverse theory of potential fields shows that the correspondence between the internal magnetic field of the Earth and its field sources is unique when the potential field is known in all points of the three-dimensional space including all points of the source region (cp., e.g. Diesselhorst, H., 1939. Magnetische Felder und Kräfte. Johann Ambrosius Barth Verlag, Leipzig). Thus, to determine the sources of the field it is not sufficient to know the potential field in the space external to the sources. Moreover, field models derived from finite sets of potential field observations emphasize different source properties because of measurement errors. In this study, I argue that improved internal field models can be developed from multi-altitude magnetic observations by imposing more effective constraints on the poorly conditioned downward continuation problem. In particular, the convergence behaviour of spherical harmonic field models can be used to improve the downward continuation of the higher truncation index terms. A high quality approximation of the field continuation is essential when the field models are interpreted for relatively small field contributions such as from the lithospheric sources. The relations between the potential field and its sources including the problems of potential field continuations - upward and downward - are governed by the theory of ill-posed inverse problems (cp., e.g. Anger, G., 1990. Inverse Problems in Differential Equations. Akademie/Plenum Press, Berlin/London; Anger, G., Gorenflo, R., Jochmann, H., Moritz, H., Webers, W. (Eds.), 1993. Inverse Problems: Principles and Applications in Geophysics, Technology, and Medicine. Akademie, Berlin; Huestis, S.P., Parker, R.L., 1979. Upward and downward continuations as inverse problems. Geophys. J. R. Astr. Soc. 57, 171-188; Rösler, R., 1981. Über die Fehlerfortpflanzung bei Potentialfeldtransformationen. Gerlands Beitr. Gephys. 90, 47-57).

  18. Geomagnetic research in the 19th century: a case study of the German contribution

    Science.gov (United States)

    Schröder, W.; Wiederkehr, K.-H.

    2001-10-01

    Even before the discovery of electromagnetism by Oersted, and before the work of Ampère, who attributed all magnetism to the flux of electrical currents, A.v. Humboldt and Hansteen had turned to geomagnetism. Through the ``Göttinger Magnetischer Verein'', a worldwide cooperation under the leadership of Gauss came into existence. Even today, Gauss's theory of geomagnetism is one of the pillars of geomagnetic research. Thereafter, J.v. Lamont, in Munich, took over the leadership in Germany. In England, the Magnetic Crusade was started by the initiative of John Herschel and E. Sabine. At the beginning of the 1840s, James Clarke Ross advanced to the vicinity of the southern magnetic pole on the Antarctic Continent, which was then quite unknown. Ten years later, Sabine was able to demonstrate solar-terrestrial relations from the data of the colonial observatories. In the 1980s, Arthur Schuster, following Balfour Stewart's ideas, succeeded in interpreting the daily variations of the electrical process in the high atmosphere. Geomagnetic research work in Germany was given a fresh impetus by the programme of the First Polar Year 1882-1883. Georg Neumayer, director of the ``Deutsche Seewarte'' in Hamburg, was one of the initiators of the Polar Year. He forged a close cooperation with the newly founded ``Kaiserliches Marineobservatorium'' in Wilhelmshaven, and also managed to gain the collaboration of the ``Gauss-Observatorium für Erdmagnetismus'' in Göttingen under E. Schering. In the Polar Year, the first automatic recording magnetometers (Kew-Model) were used in the German observatory at Wilhelmshaven. Here, M. Eschenhagen, who later became director of the geomagnetic section in the new Meteorological Magnetic Observatory in Potsdam, deserves special credit. Early hypotheses of geomagnetism and pioneering palaeomagnetic experiments are briefly reviewed. The essential seismological investigations at the turn of the 19th to the 20th century are also briefly described as

  19. Stable amorphous semiconductors for solar cells. Final report; Stabile amorphe Halbleiterfilme fuer Solarzellen. Schlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Fuhs, W.; Lips, K.; Mell, H.; Stachowitz, R.; Will, S.; Ulber, I.

    1997-12-31

    Elektronenspinresonanz (ESR), photothermische Deflektionsspektroskopie (PDS) und Photoleitungsspektroskopie (CPM) zur Verfuegung. Die Rolle der vorhandenen und zusaetzlich erzeugten Defekte auf den Rekombinationsmechanismus wurde an Filmen und Solarzellenstrukturen untersucht. Dazu wurden vor allem Photolumineszenz, frequenzaufgeloeste Photolumineszenzspektroskopie (FRS) und elektrisch detektierte magnetische Resonanz (EDMR) eingesetzt. Die Ergebnisse der Arbeiten wurden in internationalen Zeitschriften publiziert und auf internationalen Konferenzen vorgetragen. (orig.)

  20. 7. Kassel symposium on energy systems technology: Renewable energy sources and efficient utilization of energy; 7. Kasseler Symposium Energie-Systemtechnik: Erneuerbare Energien und rationelle Energieverwendung

    Energy Technology Data Exchange (ETDEWEB)

    Caselitz, P. (comp.)

    2002-07-01

    ); Doppelschichtkondensatoren - Technik, Kosten, Perspektiven (Ruediger Koetz); Einsatz von Superkondensatoren in Kraftfahrzeugen (Rainer Knorr); Supraleitende magnetische Energiespeicher (Klaus-Peter Juengst); Schwungradspeicher - Stand der Technik (Frank Taeubner); Dezentrale Energiespeicher im europaeischen Verbundsnetz - EU-Projekt DISPOWER (J. Schmid, etc.); Interkontinentale Stromverbuende - Perspektiven einer Vollversorgung Europas mit Strom aus regenerativen Quellen (Gregor Czisch); Hochspannungs-Gleichstrom-Uebertragung fuer das europaeische Verbundnetz (Michael Haeusler); Supraleitung und Energietransport - Stand der Technik und Perspektiven (Frank Schmidt).

  1. Design requirements to magnetic bearings for primary circuit blowers of high-temperature reactors. Final report; Auslegungsanforderungen an Magnetlager fuer Primaerkuehlgasgeblaese von Hochtemperaturreaktoren. Schlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    1992-02-12

    To study the operational behaviour of blower shafts with magnetic bearings, a modular computer model was set up based on model laws, which permits to simulate shaft behaviour during dynamic loads acting on the blower shaft. During simulation runs, essential properties of position regulation (guide behaviour, secondary behaviour, and fault behaviour), and the behaviour of the blower shaft in the event of failure of a final stage of magnetic bearing electronics, with not-single-failure-proof and with failure-tolerant design of the final stages, as well as the effects of mechanical vibrations, e.g. as a result of earthquakes, on the behaviour of blower shafts were investigated. In order to transfer the results of the catch bearing tests to other designs of blowers with a vertical blower shaft, transmission laws and procedures were derived from theoretical considerations and from a dimension analysis which, however, could not be verified by means of tests. Application of the test results to horizontally placed blower shafts is possible only in part. The computer simulation model set up for the behaviour of the blower shafts is applicable without significant limitations to other blower shaft arrangements. (orig.). [Deutsch] Zur Untersuchung des Betriebsverhaltens magnetisch gelagerter Geblaesewellen wurde anhand von Modellgesetzen ein modulares Rechenmodell aufgebaut, das die Simulation des Wellenverhaltens bei auf die Geblaesewelle wirkenden dynamischen Belastungen erlaubt. In Simulationslaeufen wurden wesentliche Eigenschaften der Lageregelung (Fuehrungsverhalten, Folgeverhalten und Stoerungsverhalten) und das Verhalten der Geblaesewellen bei Ausfall einer Endstufe der Magnetlagerelektronik bei nicht einzelfehlersicherer und bei fehlertoleranter Ausfuehrung der Endstufen sowie die Auswirkungen mechanischer Erschuetterungen z.B. infolge von Erdbeben auf das Verhalten der Geblaesewelle untersucht. Zur Uebertragung der Ergebnisse der Fanglagerversuche auf andere

  2. Quantitative perfusion imaging in magnetic resonance imaging; Quantitative Perfusionsbildgebung in der Magnetresonanztomographie

    Energy Technology Data Exchange (ETDEWEB)

    Zoellner, F.G.; Gaa, T.; Zimmer, F. [Universitaet Heidelberg, Computerunterstuetzte Klinische Medizin, Medizinische Fakultaet Mannheim, Mannheim (Germany); Ong, M.M.; Riffel, P.; Hausmann, D.; Schoenberg, S.O.; Weis, M. [Universitaet Heidelberg, Institut fuer Klinische Radiologie und Nuklearmedizin, Universitaetsmedizin Mannheim, Medizinische Fakultaet Mannheim, Mannheim (Germany)

    2016-02-15

    Magnetic resonance imaging (MRI) is recognized for its superior tissue contrast while being non-invasive and free of ionizing radiation. Due to the development of new scanner hardware and fast imaging techniques during the last decades, access to tissue and organ functions became possible. One of these functional imaging techniques is perfusion imaging with which tissue perfusion and capillary permeability can be determined from dynamic imaging data. Perfusion imaging by MRI can be performed by two approaches, arterial spin labeling (ASL) and dynamic contrast-enhanced (DCE) MRI. While the first method uses magnetically labelled water protons in arterial blood as an endogenous tracer, the latter involves the injection of a contrast agent, usually gadolinium (Gd), as a tracer for calculating hemodynamic parameters. Studies have demonstrated the potential of perfusion MRI for diagnostics and also for therapy monitoring. The utilization and application of perfusion MRI are still restricted to specialized centers, such as university hospitals. A broad application of the technique has not yet been implemented. The MRI perfusion technique is a valuable tool that might come broadly available after implementation of standards on European and international levels. Such efforts are being promoted by the respective professional bodies. (orig.) [German] Die Magnetresonanztomographie (MRT) zeichnet sich durch einen ueberlegenen Gewebekontrast aus, waehrend sie nichtinvasiv und frei von ionisierender Strahlung ist. Sie bietet Zugang zu Gewebe- und Organfunktion. Eine dieser funktionellen bildgebenden Verfahren ist die Perfusionsbildgebung. Mit dieser Technik koennen u. a. Gewebeperfusion und Kapillarpermeabilitaet aus dynamischen Bilddaten bestimmt werden. Perfusionsbildgebung mithilfe der MRT kann durch 2 Ansaetze, naemlich ''arterial spin labeling'' (ASL) und dynamische kontrastverstaerkte (DCE-)MRT durchgefuehrt werden. Waehrend die erste Methode magnetisch

  3. Deuterium/hydrogen isotope exchange on beryllium and beryllium nitride; Deuterium/Wasserstoff-Isotopenaustausch an Beryllium und Berylliumnitrid

    Energy Technology Data Exchange (ETDEWEB)

    Dollase, Petra; Eichler, Michael; Koeppen, Martin; Dittmar, Timo; Linsmeier, Christian [Forschungszentrum Juelich GmbH, Institut fuer Energie- und Klimaforschung - Plasmaphysik (Germany)

    2016-07-01

    In the fusion experiments JET and ITER, the first wall is made up of beryllium. The use of nitrogen is discussed for radiative cooling in the divertor. This can react with the surface of the first wall to form beryllium nitride (Be{sub 3}N{sub 2}). The hydrogen isotopes deuterium and tritium, which react in the fusion reaction to helium and a neutron, are used as fuel. Since the magnetic confinement of the plasma is not perfect, deuterium and tritium ions are also found on the beryllium wall and can accumulate there. This should be avoided due to the radioactivity of tritium. Therefore the isotope exchange with deuterium is investigated to regenerate the first wall. We investigate the isotopic exchange of deuterium and protium in order to have not to work with radioactive tritium. The ion bombardment is simulated with an ion source. With voltages up to a maximum of 5 kV, deuterium and protic hydrogen ions are implanted in polycrystalline Be and Be{sub 3}N{sub 2}. The samples are then analyzed in situ using X-ray photoelectron spectroscopy (XPS) and thermal desorption spectroscopy (TDS). Subsequently, samples prepared under the same conditions are characterized ex-situ by means of nuclear reaction analysis (NRA). [German] In den Fusionsexperimenten JET und ITER besteht die erste Wand im Hauptraum aus Beryllium (Be). Zur Strahlungskuehlung im Divertor wird der Einsatz von Stickstoff diskutiert. Dieser kann mit der Oberflaeche der ersten Wand zu Berylliumnitrid (Be{sub 3}N{sub 2}) reagieren. Als Brennstoff werden die Wasserstoffisotope Deuterium und Tritium eingesetzt, die in der Fusionsreaktion zu Helium und einem Neutron reagieren. Da der magnetische Einschluss des Plasmas nicht perfekt ist, treffen auch Deuterium- und Tritiumionen auf die Berylliumwand auf und koennen sich dort anreichern. Das soll aufgrund der Radioaktivitaet von Tritium unbedingt vermieden werden. Daher wird zur Regenerierung der ersten Wand der Isotopenaustausch mit Deuterium untersucht. Wir

  4. Structural and electronic properties of binary amorphous aluminum alloys with transition metals and rare earth metals; Strukturelle und elektronische Eigenschaften binaerer amorpher Aluminiumlegierungen mit Uebergangsmetallen und Metallen der Seltenen Erden

    Energy Technology Data Exchange (ETDEWEB)

    Stiehler, Martin

    2012-02-03

    occurs in liquid, pure elements. The goal is to build up a resonance between the static structure and the electronic system, which is associated with an average valence of 1.5 electrons per atom. The structures of the investigated amorphous Al-rare earth alloys are also correlated over large concentration ranges with an average valence of 1.5 electrons per atom. [German] Der Einfluss der d-Zustaende der Uebergangsmetalle auf die Strukturbildung in amorphen Legierungen ist bisher nur unzureichend verstanden. Die vorliegende Arbeit hat zum Ziel, zusaetzliche Beitraege zum Verstaendnis am Beispiel binaerer amorpher Aluminiumlegierungen mit Uebergangsmetallen zu erarbeiten. Speziell standen dabei Legierungen mit einer Untergruppe der Uebergangsmetalle, den Metallen der Seltenen Erden, im Vordergrund. Im Rahmen der vorliegenden Arbeit wurden Schichten von Al-Ce im Bereich von 15at%Ce-80at%Ce durch sequentielle Flash-Verdampfung bei 4,2K im Hochvakuum hergestellt und durch Messungen des elektrischen Widerstands und des Hall-Effekts elektronisch, sowie durch Transmissionselektronenbeugung strukturell charakterisiert. Ergaenzend wurden Untersuchungen der Plasmaresonanz mittels Elektronenenergieverlustspektroskopie durchgefuehrt. Im Bereich 25at%Ce-60at%Ce entstanden homogen amorphe Proben. Besonders die Strukturuntersuchungen wurden durch eine Oxidation des Materials erschwert. Der Einfluss der Ce-4f-Elektronen manifestiert sich vor allem im Tieftemperatur- und Magnetowiderstand, die beide vom Kondo-Effekt dominiert werden. Der Hall-Effekt in Al-Ce wird im gesamten untersuchten Temperaturbereich (2K-320K) von anomalen Anteilen dominiert, welche skew-scattering-Effekten, ebenfalls aufgrund der Ce-4f-Elektronen, zugeschrieben werden. Bis hinunter zu 2K trat keine makroskopische magnetische Ordnung auf. Im Bereich 2K-20K wird auf das Vorliegen von Clustern geordneter magnetischer Momente geschlossen. Fuer T>20K tritt paramagnetisches Verhalten auf. Hinsichtlich der strukturellen

  5. Broadband grating couplers for efficient thin film solar cells. Final report; Breitband-Gitterkoppler fuer effiziente Duennschichtsolarzellen. Abschlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Stutzmann, M.; Nebel, C.E.; Eisele, C.; Klein, S.; Carius, R.; Finger, F.; Schubert, M.

    2002-08-01

    tunable means of coupling sunlight into thin film solar cells. While the best results achieved so far do not give rise to a noticeable improvement compared to light trapping strategies based on statistical texture, the transferability of the process developed here to other solar cell structures is an important advantage. (ii) Thin microcrystalline SiGe-layers on glass produced by evaporation and laser crystallization exhibit promising electronic and optical properties with respect to applications as absorber layers in thin film solar cells. However, to this end, a further optimization of the crystallization process and the ensuing material properties will be necessary. (orig.) [German] Fuer Duennschicht-Solarzellen ist im Allgemeinen eine integrierte Lichtfallenstruktur notwendig, um eine moeglichst vollstaendige Absorption des Sonnenspektrums zu erzielen. Gegenwaertig werden hierfuer fast ausschliesslich statistisch texturierte transparente Elektrodenschichten (z.B. aus ZnO) eingesetzt. Ziel dieses Projektes war die Herstellung und Untersuchung mikrostrukturierter periodischer Gitterkoppler zur gezielten Einkopplung schwach absorbierten Lichtes. Zusaetzlich sollten erste Versuche zum Einsatz von kristallinen SiGe-Duennschicht-Filmen auf Glas als stark absorbierendes Halbleitermaterial fuer den Einsatz in Tandem-Solarzellen exploratorisch durchgefuehrt werden. Im Rahmen des Forschungsprojektes wurden strukturierte Elektroden aus TCO hergestellt, die hohe optische Transparenz bis ins UV aufweisen. Zur effizienten Lichteinkopplung wurden erfolgreich Beugungsgitter im Submikrometerbereich hergestellt, die als Lichtfallen wirken. In Zusammenarbeit mit dem Institut fuer Photovoltaik (IPV) wurden diese Lichtfallen in Solarzellen integriert. Die elektrischen und optischen Eigenschaften dieser Solarzellen mit Gitterkoppler-Strukturen wurden systematisch untersucht, insbesondere auch hinsichtlich einer durch die Strukturierung bewirkten internen Feldverstaerkung. Zusaetzlich

  6. Institute of Toxicology. 1994 annual report on research and development; Institut fuer Toxikologie. Ergebnisbericht ueber Forschung und Entwicklung 1994

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-12-31

    beteiligten Signalprozesse. Parallel dazu wird der Versuch einer Quantifizierung und Klassifizierung der Toxizitaet umweltrelevanter Schwermetallverbindungen unternommen. Ein wesentliches Ziel der Arbeiten ist weiterhin die Aufklaerung der Pathogenese von Lungenerkrankungen durch Staeube, Gase und Gas-Staubgemische anhand der Freisetzung von Entzuendungsstoffen durch immunologische Abwehrzellen Alveolar-Makrophagen. Mit Hilfe der Atom-Kraft-Mikroskopie sollen dynamische Veraenderungen an Zellen des Bronchialtraktes mit hoher Aufloesung dargestellt werden. Durch Untersuchungen zur Lokalisation und Struktur des Fe-Mo-Kofaktors in der Nitrogenase mit der Methode der gestoerten Winkel-Korrelationen wird ausserdem ein Beitrag zum DFG-Schwerpunktsprogramm ``Bioanorganische Chemie`` geleistet. Hauptziel des Vorhabens Biophysik multizellulaerer Systeme ist die Entwicklung fortgeschrittener Zellkultursysteme, mit denen das Toxizitaetsverhalten von Zellen unter Gewebe- und Organ-nahen Bedingungen erfasst werden kann und denen sich auch bei der Herstellung von Arzneimitteln oder im Rahmen therapeutischer Anwendungen ein breites Anwendungsfeld eroeffnet. Desweiteren werden experimentelle und theoretische Arbeiten zur zellulaeren Wirkung langsam veraenderlicher elektrischer und magnetischer Felder durchgefuehrt. (orig./MG)